[Osiris]

The file uxtheme.dll is a digitally signed file that validates themes during boot and theme installation. It is restricted and usually means that you can only install a handful of Microsoft certified themes. If you want to add and use custom themes in Windows XP or Windows Vista you have to update the file uxtheme.dll. Once the file is patched you can install and use custom themes.
I would like to introduce two methods of patching uxtheme.dll. The first method is automatic but sometimes not working. I would still suggest to use the Uxtheme Multi-patcher first if you use Windows XP or Windows Server 2003. Just unpack and start the application (no installation required) and click on Patch to patch uxtheme.dll. The software checks the operating system and asks if the findings are correct. If the information is correct click OK.
Windows File Protection will kick in which you have to cancel of course. File Protection would otherwise replace the patched uxtheme.dll with the original from the Windows XP CD which would have the result that you would not be able to use custom themes. Once that is done restart the computer once and check if you can add custom themes. If that is possible you have successfully patched uxtheme.dll. If not or if you are using Windows Vista read on.
Windows Vista users or users where the automatic patching failed can replace the file manually instead. They need the application Replacer for it which can be used to replace files with system protection. They also need the patched uxtheme.dll which they can find at Uxtheme Patches. Make sure to download the correct version for your operating system.
Start Replacer and follow the on screen instructions. Begin by dragging and dropping the original uxtheme.dll file which is located in c:\windows\system32 into the program window and hit enter. Then drag and drop the patched dll into the window and hit enter again. Follow the instructions until File Protection kicks in again. Make sure you cancel the file protection window so that the patched file is not replaced with the original one again.
Custom themes can be added after a restart.

Welcome To Tech-Dump

[Mak213]

Sadly this can not be done with Vista SP1. There were changes made to it and if you replace it you will lose all themes but classic.