diff --git a/trunk/ProcessHacker.Native/OSVersion.cs b/trunk/ProcessHacker.Native/OSVersion.cs
index 14f83e652..8969d6af2 100644
--- a/trunk/ProcessHacker.Native/OSVersion.cs
+++ b/trunk/ProcessHacker.Native/OSVersion.cs
@@ -36,10 +36,10 @@ namespace ProcessHacker.Native
         /// <summary>
         /// Windows 2000.
         /// </summary>
-        Win2000 = 50,
+        TwoThousand = 50,
 
         /// <summary>
-        /// Windows XP SP2, SP3.
+        /// Windows XP.
         /// </summary>
         XP = 51,
 
@@ -49,24 +49,19 @@ namespace ProcessHacker.Native
         Server2003 = 52,
 
         /// <summary>
-        /// Windows Vista SP0, SP1, SP2, Windows Server 2008.
+        /// Windows Vista, Windows Server 2008.
         /// </summary>
         Vista = 60,
 
         /// <summary>
-        /// Windows 7 SP0.
+        /// Windows 7, Windows Server 2008 R2.
         /// </summary>
         Seven = 61,
 
         /// <summary>
-        /// An unreleased version of Windows.
+        /// An unknown version of Windows.
         /// </summary>
-        Unreleased = int.MaxValue,
-
-        /// <summary>
-        /// An unsupported version of Windows.
-        /// </summary>
-        Unsupported = int.MinValue
+        Unknown = int.MaxValue
     }
 
     public static class OSVersion
@@ -86,6 +81,7 @@ namespace ProcessHacker.Native
         private static bool _hasQueryLimitedInformation = false;
         private static bool _hasSetAccessToken = false;
         private static bool _hasTaskDialogs = false;
+        private static bool _hasThemes = false;
         private static bool _hasUac = false;
         private static bool _hasWin32ImageFileName = false;
 
@@ -93,66 +89,23 @@ namespace ProcessHacker.Native
         {
             System.Version version = Environment.OSVersion.Version;
 
-            switch (version.Major)
-            {
-                case 5:
-                    {
-                        switch (version.Minor)
-                        {
-                            case 0:
-                                _windowsVersion = WindowsVersion.Win2000;
-                                break;
-                            case 1:
-                                _windowsVersion = WindowsVersion.XP;
-                                break;
-                            case 2:
-                                _windowsVersion = WindowsVersion.Server2003;
-                                break;
-                            default:
-                                break; //Not detected, jump to version.Major default
-                        }
-                        break;
-                    }
-                case 6:
-                    {
-                        switch (version.Minor)
-                        {
-                            case 0:
-                                _windowsVersion = WindowsVersion.Vista;
-                                break;
-                            case 1:
-                                _windowsVersion = WindowsVersion.Seven;
-                                break;
-                            default:
-                                break; //Not detected, jump to version.Major default
-                        }
-                        break;
-                    }
-                default:
-                    if (version.Major > 6 || version.Minor > 1) //check if newer than latest Windows release
-                    {
-                        _windowsVersion = WindowsVersion.Unreleased;
-                        break;
-                    }
-                    else //OS version not detected and not newer than the newest Windows release
-                        _windowsVersion = WindowsVersion.Unsupported;
-                        break;
-            }
+            if (version.Major == 5 && version.Minor == 0)
+                _windowsVersion = WindowsVersion.TwoThousand;
+            else if (version.Major == 5 && version.Minor == 1)
+                _windowsVersion = WindowsVersion.XP;
+            else if (version.Major == 5 && version.Minor == 2)
+                _windowsVersion = WindowsVersion.Server2003;
+            else if (version.Major == 6 && version.Minor == 0)
+                _windowsVersion = WindowsVersion.Vista;
+            else if (version.Major == 6 && version.Minor == 1)
+                _windowsVersion = WindowsVersion.Seven;
+            else
+                _windowsVersion = WindowsVersion.Unknown;
 
-            //if (version.Major == 5 && version.Minor == 0)
-            //    _windowsVersion = WindowsVersion.Win2000;
-            //else if (version.Major == 5 && version.Minor == 1)
-            //    _windowsVersion = WindowsVersion.XP;
-            //else if (version.Major == 5 && version.Minor == 2)
-            //    _windowsVersion = WindowsVersion.Server2003;
-            //else if (version.Major == 6 && version.Minor == 0)
-            //    _windowsVersion = WindowsVersion.Vista;
-            //else if (version.Major == 6 && version.Minor == 1)
-            //    _windowsVersion = WindowsVersion.Seven;
-            //else if ((version.Major == 6 && version.Minor > 1) || version.Major > 6)
-            //    _windowsVersion = WindowsVersion.Unreleased;
-            //else
-            //    _windowsVersion = WindowsVersion.Unsupported;
+            if (IsAboveOrEqual(WindowsVersion.XP))
+            {
+                _hasThemes = true;
+            }
 
             if (IsBelow(WindowsVersion.Vista))
             {
@@ -250,6 +203,11 @@ namespace ProcessHacker.Native
             get { return _hasTaskDialogs; }
         }
 
+        public static bool HasThemes
+        {
+            get { return _hasThemes; }
+        }
+
         public static bool HasUac
         {
             get { return _hasUac; }
diff --git a/trunk/ProcessHacker/Common/PhUtils.cs b/trunk/ProcessHacker/Common/PhUtils.cs
index 48b53f9f2..98790f5b4 100644
--- a/trunk/ProcessHacker/Common/PhUtils.cs
+++ b/trunk/ProcessHacker/Common/PhUtils.cs
@@ -382,7 +382,11 @@ namespace ProcessHacker.Common
         /// <param name="theme">A name of a theme.</param>
         public static void SetTheme(this Control control, string theme)
         {
-            Win32.SetWindowTheme(control.Handle, theme, null);
+            // Don't set on XP, doesn't look better than without SetWindowTheme.
+            if (OSVersion.IsAboveOrEqual(WindowsVersion.Vista))
+            {
+                Win32.SetWindowTheme(control.Handle, theme, null);
+            }
         }
 
         /// <summary>
diff --git a/trunk/ProcessHacker/Components/ExtendedTreeView.cs b/trunk/ProcessHacker/Components/ExtendedTreeView.cs
index a2f67aea7..5be7160e2 100644
--- a/trunk/ProcessHacker/Components/ExtendedTreeView.cs
+++ b/trunk/ProcessHacker/Components/ExtendedTreeView.cs
@@ -43,9 +43,9 @@ namespace ProcessHacker.Components
             if (OSVersion.IsAboveOrEqual(WindowsVersion.Vista))
             {
                 Win32.SendMessage(this.Handle, (WindowMessage)TVM_SETEXTENDEDSTYLE, 0, TVS_EX_FADEINOUTEXPANDOS);
-                HResult setThemeResult = Win32.SetWindowTheme(this.Handle, "explorer", null);
-                setThemeResult.ThrowIf();
+                ProcessHacker.Common.PhUtils.SetTheme(this, "explorer");
             }
+
             base.OnHandleCreated(e);
         }
     }
diff --git a/trunk/ProcessHacker/Program/Program.cs b/trunk/ProcessHacker/Program/Program.cs
index 6c29b1bcc..d8c439e7c 100644
--- a/trunk/ProcessHacker/Program/Program.cs
+++ b/trunk/ProcessHacker/Program/Program.cs
@@ -119,25 +119,20 @@ namespace ProcessHacker
             Application.EnableVisualStyles();
             Application.SetCompatibleTextRenderingDefault(false);
 
-            //before parsing commandline arguments, check OS support.
-            if (OSVersion.IsBelow(WindowsVersion.Win2000))
-            {
-                PhUtils.ShowError("This Operating System is not supported!");
-                Environment.Exit(1);
-            }
-            else if (OSVersion.WindowsVersion == WindowsVersion.Unreleased)
-            {
-                PhUtils.ShowError("This Operating System is unreleased and not currently supported," + 
-                    "\nProcess Hacker support has not been tested so expect bugs and issues.");
-            }
-
             if (Environment.Version.Major < 2)
             {
                 PhUtils.ShowError("You must have .NET Framework 2.0 or higher to use Process Hacker.");
                 Environment.Exit(1);
             }
 
-#if !DEBUG            
+            // Check OS support.
+
+            if (OSVersion.IsBelow(WindowsVersion.TwoThousand) || OSVersion.IsAbove(WindowsVersion.Seven))
+            {
+                PhUtils.ShowWarning("Your operating system is not supported by Process Hacker.");
+            }
+
+#if !DEBUG
             // Setup exception handling at first opportunity to catch exceptions generatable anywhere.
             Application.ThreadException += new ThreadExceptionEventHandler(Application_ThreadException);
             AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException);