diff --git a/xpinstall/wizard/windows/setup/extra.c b/xpinstall/wizard/windows/setup/extra.c
index 3e977f2a7b7d..400b5e3ee51c 100644
--- a/xpinstall/wizard/windows/setup/extra.c
+++ b/xpinstall/wizard/windows/setup/extra.c
@@ -7948,11 +7948,31 @@ HRESULT DecryptVariable(LPSTR szVariable, DWORD dwVariableSize)
   {
     /* parse for the "c:\Program Files" directory */
     GetWinReg(HKEY_LOCAL_MACHINE, szWRMSCurrentVersion, "ProgramFilesDir", szVariable, dwVariableSize);
+    /* see if that failed */
+    if (*szVariable == 0)
+    {
+      char* backslash;
+      /* Use the parent of the windows directory */
+      GetWindowsDirectory(szVariable, dwVariableSize);
+      backslash = strrchr(szVariable, '\\');
+      if (backslash)
+        *backslash = 0;
+    }
   }
   else if(lstrcmpi(szVariable, "PROGRAMFILESPATH") == 0)
   {
     /* parse for the "\Program Files" directory -- NOTE does not include the drive letter */
     GetWinReg(HKEY_LOCAL_MACHINE, szWRMSCurrentVersion, "ProgramFilesDir", szBuf, sizeof(szBuf));
+    /* see if that failed */
+    if (*szBuf == 0)
+    {
+      char* backslash;
+      /* Use the parent of the windows directory */
+      GetWindowsDirectory(szBuf, sizeof(szBuf));
+      backslash = strrchr(szBuf, '\\');
+      if (backslash)
+        *backslash = 0;
+    }
     lstrcpy(szVariable, szBuf+2);
   }
   else if(lstrcmpi(szVariable, "INSTALLDRIVE") == 0)
diff --git a/xpinstall/wizard/windows/uninstall/extra.c b/xpinstall/wizard/windows/uninstall/extra.c
index 7b5803a5288a..ff97e6535c90 100644
--- a/xpinstall/wizard/windows/uninstall/extra.c
+++ b/xpinstall/wizard/windows/uninstall/extra.c
@@ -2202,6 +2202,16 @@ HRESULT DecryptVariable(LPSTR szVariable, DWORD dwVariableSize)
   {
     /* parse for the "c:\Program Files" directory */
     GetWinReg(HKEY_LOCAL_MACHINE, "Software\\Microsoft\\Windows\\CurrentVersion", "ProgramFilesDir", szVariable, dwVariableSize);
+    /* see if that failed */
+    if (*szVariable == 0)
+    {
+      char* backslash;
+      /* Use the parent of the windows directory */
+      GetWindowsDirectory(szVariable, dwVariableSize);
+      backslash = strrchr(szVariable, '\\');
+      if (backslash)
+        *backslash = 0;
+    }
   }
   else if(lstrcmpi(szVariable, "COMMONFILESDIR") == 0)
   {