diff --git a/dlls/devenum/createdevenum.c b/dlls/devenum/createdevenum.c
index 4a2e101bf00..625ff623f38 100644
--- a/dlls/devenum/createdevenum.c
+++ b/dlls/devenum/createdevenum.c
@@ -258,7 +258,7 @@ static void DEVENUM_ReadPins(HKEY hkeyFilterClass, REGFILTER2 *rgf2)
         WCHAR wszPinName[MAX_PATH];
         DWORD cName = sizeof(wszPinName) / sizeof(WCHAR);
         DWORD Type, cbData;
-        REGFILTERPINS *rgPin = &rgPins[rgf2->u.s.cPins];
+        REGFILTERPINS *rgPin = &rgPins[rgf2->u.s1.cPins];
         LONG lRet;
 
         rgPin->strName = NULL;
@@ -298,7 +298,7 @@ static void DEVENUM_ReadPins(HKEY hkeyFilterClass, REGFILTER2 *rgf2)
 
         DEVENUM_ReadPinTypes(hkeyPinKey, rgPin);
 
-        ++rgf2->u.s.cPins;
+        ++rgf2->u.s1.cPins;
         continue;
 
         error_cleanup:
@@ -309,13 +309,13 @@ static void DEVENUM_ReadPins(HKEY hkeyFilterClass, REGFILTER2 *rgf2)
 
     RegCloseKey(hkeyPins);
 
-    if (rgPins && !rgf2->u.s.cPins)
+    if (rgPins && !rgf2->u.s1.cPins)
     {
         CoTaskMemFree(rgPins);
         rgPins = NULL;
     }
 
-    rgf2->u.s.rgPins = rgPins;
+    rgf2->u.s1.rgPins = rgPins;
 }
 
 static HRESULT DEVENUM_RegisterLegacyAmFilters(void)
@@ -386,8 +386,8 @@ static HRESULT DEVENUM_RegisterLegacyAmFilters(void)
 
                 rgf2.dwVersion = 1;
                 rgf2.dwMerit = 0;
-                rgf2.u.s.cPins = 0;
-                rgf2.u.s.rgPins = NULL;
+                rgf2.u.s1.cPins = 0;
+                rgf2.u.s1.rgPins = NULL;
 
                 cbData = sizeof(wszFilterName);
                 if (RegQueryValueExW(hkeyFilterClass, NULL, NULL, &Type, (LPBYTE)wszFilterName, &cbData) != ERROR_SUCCESS ||
@@ -413,29 +413,29 @@ static HRESULT DEVENUM_RegisterLegacyAmFilters(void)
 
                 if (hkeyFilterClass) RegCloseKey(hkeyFilterClass);
 
-                if (rgf2.u.s.rgPins)
+                if (rgf2.u.s1.rgPins)
                 {
                     UINT iPin;
 
-                    for (iPin = 0; iPin < rgf2.u.s.cPins; iPin++)
+                    for (iPin = 0; iPin < rgf2.u.s1.cPins; iPin++)
                     {
-                        CoTaskMemFree(rgf2.u.s.rgPins[iPin].strName);
+                        CoTaskMemFree(rgf2.u.s1.rgPins[iPin].strName);
 
-                        if (rgf2.u.s.rgPins[iPin].lpMediaType)
+                        if (rgf2.u.s1.rgPins[iPin].lpMediaType)
                         {
                             UINT iType;
 
-                            for (iType = 0; iType < rgf2.u.s.rgPins[iPin].nMediaTypes; iType++)
+                            for (iType = 0; iType < rgf2.u.s1.rgPins[iPin].nMediaTypes; iType++)
                             {
-                                CoTaskMemFree((void*)rgf2.u.s.rgPins[iPin].lpMediaType[iType].clsMajorType);
-                                CoTaskMemFree((void*)rgf2.u.s.rgPins[iPin].lpMediaType[iType].clsMinorType);
+                                CoTaskMemFree((void*)rgf2.u.s1.rgPins[iPin].lpMediaType[iType].clsMajorType);
+                                CoTaskMemFree((void*)rgf2.u.s1.rgPins[iPin].lpMediaType[iType].clsMinorType);
                             }
 
-                            CoTaskMemFree((void*)rgf2.u.s.rgPins[iPin].lpMediaType);
+                            CoTaskMemFree((void*)rgf2.u.s1.rgPins[iPin].lpMediaType);
                         }
                     }
 
-                    CoTaskMemFree((void*)rgf2.u.s.rgPins);
+                    CoTaskMemFree((void*)rgf2.u.s1.rgPins);
                 }
             }
         }
@@ -604,8 +604,8 @@ static HRESULT DEVENUM_CreateSpecialCategories(void)
 
     rf2.dwVersion = 2;
     rf2.dwMerit = MERIT_PREFERRED;
-    rf2.u.s1.cPins2 = 1;
-    rf2.u.s1.rgPins2 = &rfp2;
+    rf2.u.s2.cPins2 = 1;
+    rf2.u.s2.rgPins2 = &rfp2;
     rfp2.cInstances = 1;
     rfp2.nMediums = 0;
     rfp2.lpMedium = NULL;
diff --git a/dlls/dxdiagn/provider.c b/dlls/dxdiagn/provider.c
index db407b08e30..1e00a90bdff 100644
--- a/dlls/dxdiagn/provider.c
+++ b/dlls/dxdiagn/provider.c
@@ -1351,16 +1351,16 @@ static HRESULT fill_filter_data_information(IDxDiagContainerImpl_Container *subc
 
     if (pRF->dwVersion == 1)
     {
-        for (j = 0; j < pRF->u.s.cPins; j++)
-            if (pRF->u.s.rgPins[j].bOutput)
+        for (j = 0; j < pRF->u.s1.cPins; j++)
+            if (pRF->u.s1.rgPins[j].bOutput)
                 dwNOutputs++;
             else
                 dwNInputs++;
     }
     else if (pRF->dwVersion == 2)
     {
-        for (j = 0; j < pRF->u.s1.cPins2; j++)
-            if (pRF->u.s1.rgPins2[j].dwFlags & REG_PINFLAG_B_OUTPUT)
+        for (j = 0; j < pRF->u.s2.cPins2; j++)
+            if (pRF->u.s2.rgPins2[j].dwFlags & REG_PINFLAG_B_OUTPUT)
                 dwNOutputs++;
             else
                 dwNInputs++;
diff --git a/dlls/quartz/filtermapper.c b/dlls/quartz/filtermapper.c
index 8950caab463..11a0bd363cf 100644
--- a/dlls/quartz/filtermapper.c
+++ b/dlls/quartz/filtermapper.c
@@ -485,24 +485,24 @@ static HRESULT FM2_WriteFilterData(const REGFILTER2 * prf2, BYTE **ppData, ULONG
 
     rrf.dwVersion = prf2->dwVersion;
     rrf.dwMerit = prf2->dwMerit;
-    rrf.dwPins = prf2->u.s1.cPins2;
+    rrf.dwPins = prf2->u.s2.cPins2;
     rrf.dwUnused = 0;
 
     add_data(&mainStore, (LPBYTE)&rrf, sizeof(rrf));
 
-    for (i = 0; i < prf2->u.s1.cPins2; i++)
+    for (i = 0; i < prf2->u.s2.cPins2; i++)
     {
         size += sizeof(struct REG_RFP);
-        if (prf2->u.s1.rgPins2[i].clsPinCategory)
+        if (prf2->u.s2.rgPins2[i].clsPinCategory)
             size += sizeof(DWORD);
-        size += prf2->u.s1.rgPins2[i].nMediaTypes * sizeof(struct REG_TYPE);
-        size += prf2->u.s1.rgPins2[i].nMediums * sizeof(DWORD);
+        size += prf2->u.s2.rgPins2[i].nMediaTypes * sizeof(struct REG_TYPE);
+        size += prf2->u.s2.rgPins2[i].nMediums * sizeof(DWORD);
     }
 
-    for (i = 0; i < prf2->u.s1.cPins2; i++)
+    for (i = 0; i < prf2->u.s2.cPins2; i++)
     {
         struct REG_RFP rrfp;
-        REGFILTERPINS2 rgPin2 = prf2->u.s1.rgPins2[i];
+        REGFILTERPINS2 rgPin2 = prf2->u.s2.rgPins2[i];
         unsigned int j;
 
         rrfp.signature[0] = '0';
@@ -604,9 +604,9 @@ static HRESULT FM2_ReadFilterData(BYTE *pData, REGFILTER2 * prf2)
 
         prf2->dwVersion = prrf->dwVersion;
         prf2->dwMerit = prrf->dwMerit;
-        prf2->u.s1.cPins2 = prrf->dwPins;
+        prf2->u.s2.cPins2 = prrf->dwPins;
         rgPins2 = CoTaskMemAlloc(prrf->dwPins * sizeof(*rgPins2));
-        prf2->u.s1.rgPins2 = rgPins2;
+        prf2->u.s2.rgPins2 = rgPins2;
         pCurrent += sizeof(struct REG_RF);
 
         for (i = 0; i < prrf->dwPins; i++)
@@ -688,21 +688,21 @@ static HRESULT FM2_ReadFilterData(BYTE *pData, REGFILTER2 * prf2)
 static void FM2_DeleteRegFilter(REGFILTER2 * prf2)
 {
     UINT i;
-    for (i = 0; i < prf2->u.s1.cPins2; i++)
+    for (i = 0; i < prf2->u.s2.cPins2; i++)
     {
         UINT j;
-        if (prf2->u.s1.rgPins2[i].clsPinCategory)
-            CoTaskMemFree((LPVOID)prf2->u.s1.rgPins2[i].clsPinCategory);
+        if (prf2->u.s2.rgPins2[i].clsPinCategory)
+            CoTaskMemFree((LPVOID)prf2->u.s2.rgPins2[i].clsPinCategory);
 
-        for (j = 0; j < prf2->u.s1.rgPins2[i].nMediaTypes; j++)
+        for (j = 0; j < prf2->u.s2.rgPins2[i].nMediaTypes; j++)
         {
-            CoTaskMemFree((LPVOID)prf2->u.s1.rgPins2[i].lpMediaType[j].clsMajorType);
-            CoTaskMemFree((LPVOID)prf2->u.s1.rgPins2[i].lpMediaType[j].clsMinorType);
+            CoTaskMemFree((LPVOID)prf2->u.s2.rgPins2[i].lpMediaType[j].clsMajorType);
+            CoTaskMemFree((LPVOID)prf2->u.s2.rgPins2[i].lpMediaType[j].clsMinorType);
         }
-        CoTaskMemFree((LPVOID)prf2->u.s1.rgPins2[i].lpMediaType);
-        CoTaskMemFree((LPVOID)prf2->u.s1.rgPins2[i].lpMedium);
+        CoTaskMemFree((LPVOID)prf2->u.s2.rgPins2[i].lpMediaType);
+        CoTaskMemFree((LPVOID)prf2->u.s2.rgPins2[i].lpMedium);
     }
-    CoTaskMemFree((LPVOID)prf2->u.s1.rgPins2);
+    CoTaskMemFree((LPVOID)prf2->u.s2.rgPins2);
 }
 
 static HRESULT WINAPI FilterMapper3_RegisterFilter(
@@ -747,24 +747,24 @@ static HRESULT WINAPI FilterMapper3_RegisterFilter(
         /* REGFILTER2 structure is converted from version 1 to 2. Tested on Win2k. */
         regfilter2.dwVersion = 2;
         regfilter2.dwMerit = prf2->dwMerit;
-        regfilter2.u.s1.cPins2 = prf2->u.s.cPins;
-        pregfp2 = CoTaskMemAlloc(prf2->u.s.cPins * sizeof(REGFILTERPINS2));
-        regfilter2.u.s1.rgPins2 = pregfp2;
-        for (i = 0; i < prf2->u.s.cPins; i++)
+        regfilter2.u.s2.cPins2 = prf2->u.s1.cPins;
+        pregfp2 = CoTaskMemAlloc(prf2->u.s1.cPins * sizeof(REGFILTERPINS2));
+        regfilter2.u.s2.rgPins2 = pregfp2;
+        for (i = 0; i < prf2->u.s1.cPins; i++)
         {
             flags = 0;
-            if (prf2->u.s.rgPins[i].bRendered)
+            if (prf2->u.s1.rgPins[i].bRendered)
                 flags |= REG_PINFLAG_B_RENDERER;
-            if (prf2->u.s.rgPins[i].bOutput)
+            if (prf2->u.s1.rgPins[i].bOutput)
                 flags |= REG_PINFLAG_B_OUTPUT;
-            if (prf2->u.s.rgPins[i].bZero)
+            if (prf2->u.s1.rgPins[i].bZero)
                 flags |= REG_PINFLAG_B_ZERO;
-            if (prf2->u.s.rgPins[i].bMany)
+            if (prf2->u.s1.rgPins[i].bMany)
                 flags |= REG_PINFLAG_B_MANY;
             pregfp2[i].dwFlags = flags;
             pregfp2[i].cInstances = 1;
-            pregfp2[i].nMediaTypes = prf2->u.s.rgPins[i].nMediaTypes;
-            pregfp2[i].lpMediaType = prf2->u.s.rgPins[i].lpMediaType;
+            pregfp2[i].nMediaTypes = prf2->u.s1.rgPins[i].nMediaTypes;
+            pregfp2[i].lpMediaType = prf2->u.s1.rgPins[i].lpMediaType;
             pregfp2[i].nMediums = 0;
             pregfp2[i].lpMedium = NULL;
             pregfp2[i].clsPinCategory = NULL;
@@ -1106,9 +1106,9 @@ static HRESULT WINAPI FilterMapper3_EnumMatchingFilters(
                     /* determine whether filter meets requirements */
                     if (SUCCEEDED(hrSub) && (rf2.dwMerit >= dwMerit))
                     {
-                        for (i = 0; (i < rf2.u.s1.cPins2) && (!bInputMatch || !bOutputMatch); i++)
+                        for (i = 0; (i < rf2.u.s2.cPins2) && (!bInputMatch || !bOutputMatch); i++)
                         {
-                            const REGFILTERPINS2 * rfp2 = rf2.u.s1.rgPins2 + i;
+                            const REGFILTERPINS2 * rfp2 = rf2.u.s2.rgPins2 + i;
 
                             bInputMatch = bInputMatch || (!(rfp2->dwFlags & REG_PINFLAG_B_OUTPUT) &&
                                 (!bRender || (rfp2->dwFlags & REG_PINFLAG_B_RENDERER)) &&
diff --git a/dlls/quartz/regsvr.c b/dlls/quartz/regsvr.c
index 22455f7c271..340dec40122 100644
--- a/dlls/quartz/regsvr.c
+++ b/dlls/quartz/regsvr.c
@@ -590,8 +590,8 @@ static HRESULT register_filters(struct regsvr_filter const *list)
 	    for (i = 0; list->pins[i].flags != 0xFFFFFFFF; i++) ;
 	    rf2.dwVersion = 2;
 	    rf2.dwMerit = list->merit;
-	    rf2.u.s1.cPins2 = i;
-	    rf2.u.s1.rgPins2 = prfp2 = CoTaskMemAlloc(i*sizeof(REGFILTERPINS2));
+	    rf2.u.s2.cPins2 = i;
+	    rf2.u.s2.rgPins2 = prfp2 = CoTaskMemAlloc(i*sizeof(REGFILTERPINS2));
 	    if (!prfp2) {
 		hr = E_OUTOFMEMORY;
 		break;
diff --git a/dlls/strmbase/dllfunc.c b/dlls/strmbase/dllfunc.c
index 5c9b8ab9b30..202cd811558 100644
--- a/dlls/strmbase/dllfunc.c
+++ b/dlls/strmbase/dllfunc.c
@@ -143,8 +143,8 @@ HRESULT WINAPI AMovieSetupRegisterFilter2(const AMOVIESETUP_FILTER *pFilter, IFi
             REGFILTER2 rf2;
             rf2.dwVersion = 1;
             rf2.dwMerit = pFilter->merit;
-            rf2.u.s.cPins = pFilter->pins;
-            rf2.u.s.rgPins = pFilter->pPin;
+            rf2.u.s1.cPins = pFilter->pins;
+            rf2.u.s1.rgPins = pFilter->pPin;
 
             return IFilterMapper2_RegisterFilter(pIFM2, pFilter->clsid, pFilter->name, NULL, &CLSID_LegacyAmFilterCategory, NULL, &rf2);
         }
diff --git a/include/amvideo.idl b/include/amvideo.idl
index ea486d5e887..37d06ff0841 100644
--- a/include/amvideo.idl
+++ b/include/amvideo.idl
@@ -204,7 +204,7 @@ typedef struct tagVIDEOINFO
         RGBQUAD bmiColors[iPALETTE_COLORS];
         DWORD dwBitMasks[iMASK_COLORS];
         TRUECOLORINFO TrueColorInfo;
-    } DUMMYUNIONNAME;
+    };
 } VIDEOINFO;
 
 typedef struct tagMPEG1VIDEOINFO
diff --git a/include/axextend.idl b/include/axextend.idl
index bf877314a3c..662d6e500d5 100644
--- a/include/axextend.idl
+++ b/include/axextend.idl
@@ -236,18 +236,18 @@ typedef struct
             {
                 ULONG cPins;
                 [size_is(cPins)] const REGFILTERPINS *rgPins;
-            } DUMMYSTRUCTNAME;
+            };
 
         [case(2)]
             struct
             {
                 ULONG cPins2;
                 [size_is(cPins2)] const REGFILTERPINS2 *rgPins2;
-            } DUMMYSTRUCTNAME1;
+            };
 
         [default]
             ;
-    } DUMMYUNIONNAME;
+    };
 
 } REGFILTER2;
 
diff --git a/include/d3d10.idl b/include/d3d10.idl
index ac9894212e7..73a9e62a650 100644
--- a/include/d3d10.idl
+++ b/include/d3d10.idl
@@ -644,7 +644,7 @@ typedef struct D3D10_DEPTH_STENCIL_VIEW_DESC {
         D3D10_TEX2D_ARRAY_DSV Texture2DArray;
         D3D10_TEX2DMS_DSV Texture2DMS;
         D3D10_TEX2DMS_ARRAY_DSV Texture2DMSArray;
-    } DUMMYUNIONNAME;
+    };
 } D3D10_DEPTH_STENCIL_VIEW_DESC;
 
 typedef enum D3D10_RTV_DIMENSION {
@@ -711,7 +711,7 @@ typedef struct D3D10_RENDER_TARGET_VIEW_DESC {
         D3D10_TEX2DMS_RTV Texture2DMS;
         D3D10_TEX2DMS_ARRAY_RTV Texture2DMSArray;
         D3D10_TEX3D_RTV Texture3D;
-    } DUMMYUNIONNAME;
+    };
 } D3D10_RENDER_TARGET_VIEW_DESC;
 
 typedef D3D_SRV_DIMENSION D3D10_SRV_DIMENSION;
@@ -777,7 +777,7 @@ typedef struct D3D10_SHADER_RESOURCE_VIEW_DESC {
         D3D10_TEX2DMS_ARRAY_SRV Texture2DMSArray;
         D3D10_TEX3D_SRV Texture3D;
         D3D10_TEXCUBE_SRV TextureCube;
-    } DUMMYUNIONNAME;
+    };
 } D3D10_SHADER_RESOURCE_VIEW_DESC;
 
 typedef struct D3D10_BOX {
diff --git a/include/devicetopology.idl b/include/devicetopology.idl
index c58a5e7c2ab..0cacce286ce 100644
--- a/include/devicetopology.idl
+++ b/include/devicetopology.idl
@@ -57,12 +57,12 @@ typedef struct
     union
     {
         struct {
-           GUID Set;
+            GUID Set;
             ULONG Id;
             ULONG Flags;
-        } DUMMYSTRUCTNAME;
+        };
         LONGLONG Alignment;
-    } DUMMYUNIONNAME;
+    };
 } KSIDENTIFIER;
 
 typedef KSIDENTIFIER KSPROPERTY, *PKSPROPERTY;
diff --git a/include/imnxport.idl b/include/imnxport.idl
index ef4f8ac4019..bd85ff490c9 100644
--- a/include/imnxport.idl
+++ b/include/imnxport.idl
@@ -435,7 +435,7 @@ interface ISMTPCallback : ITransportCallback
         {
         [case(SMTP_SEND_STREAM)]    SMTPSTREAM rStreamInfo;
         [default];
-        } DUMMYUNIONNAME;
+        };
     } SMTPRESPONSE, *LPSMTPRESPONSE;
 
     HRESULT OnResponse(
@@ -606,7 +606,7 @@ interface IPOP3Callback : ITransportCallback
         [case(POP3_RETR)] POP3RETR rRetrInfo;
         [case(POP3_TOP)]  POP3TOP rTopInfo;
         [default];
-        } DUMMYUNIONNAME;
+        };
     } POP3RESPONSE, *LPPOP3RESPONSE;
 
     HRESULT OnResponse(
diff --git a/include/propidl.idl b/include/propidl.idl
index e2da625fb44..3fc7515a6bf 100644
--- a/include/propidl.idl
+++ b/include/propidl.idl
@@ -201,7 +201,7 @@ interface IPropertyStorage : IUnknown
     [case(VT_BYREF|VT_DISPATCH)]          IDispatch **ppdispVal;
     [case(VT_BYREF|VT_ARRAY)]             LPSAFEARRAY *pparray;
     [case(VT_BYREF|VT_VARIANT)]           PROPVARIANT *pvarVal;
-    } DUMMYUNIONNAME;
+    };
   };
 
   typedef struct tagPROPVARIANT *LPPROPVARIANT;