Work around a WPF issue when %WINDIR% is set to an incorrect path

src/Main/StartUp/Project/SharpDevelopMain.cs

@@ -120,6 +120,11 @@ namespace ICSharpCode.SharpDevelop
 				MessageBox.Show("This version of SharpDevelop requires .NET 4.0. You are using: " + Environment.Version, "SharpDevelop");
 				return false;
 			}
+			// Work around a WPF issue when %WINDIR% is set to an incorrect path
+			string windir = Environment.GetFolderPath(Environment.SpecialFolder.Windows, Environment.SpecialFolderOption.DoNotVerify);
+			if (Environment.GetEnvironmentVariable("WINDIR") != windir) {
+				Environment.SetEnvironmentVariable("WINDIR", windir);
+			}
 			return true;
 		}