IMPORTANT NOTE
You will need the following file to perform the instructions below:  uxthemedll_sp2.zip ( 111.85k ) Number of downloads: 1314

This file is the patched uxtheme.dll file for Windows Service Pack 2
DO NOT attempt to use this dll file with any other version of XP EXCEPT for SP2. Doing so will render your system unbootable. If you have SP1 or no SP installed, you will have to obtain the patched uxtheme.dll for those XP versions elsewhere first, and then complete the instructions below. Alternatively, you can use this tutorial to patch your uxtheme.dll automatically regardless of what version of XP you run....

Here's quick and dirty instructions for replacing the uxtheme.dll file installed by XP Service Pack 2 with the patched version available here

Open Windows Explorer and copy c:\windows\system32\uxtheme.dll to c:\windows\system32\uxtheme.bak
Still in Windows Explorer, copy the patched uxtheme.dll (included in the zip at the beginning of this article) to c:\
Insert your Windows XP installation CD into your CDROM drive.
Reboot your computer and enter the BIOS. Set your first boot device to CDROM.
Reboot again. Hit enter when prompted to boot off CDROM (most systems should just boot off the CDROM automatically).
Let Windows XP begin installation process. Don't do anything when prompted to hit F2 or F6. Wait until you get the first prompt asking you what you want to do.
Hit 'R' on your keyboard to enter the Recovery Console.
When prompted, select which Windows you want to logon to. Hit '1' on your keyboard unless you have a multi-boot setup. In this case, select your XP installation.
When prompted, enter the Administrator password.
At the command prompt, copy the patched uxtheme.dll file overtop of the existing file in the system32 directory. To do this execute these commands in order. (enter) means hit the Enter button on your keyboard):

cd c:\(enter)
copy c:\uxtheme.dll c:\windows\system32(enter)

Windows will prompt you:

Overwrite c:\windows\system32\uxtheme.dll? (Yes/No/All):

Type:

yes(enter)
exit(enter)

Your system should automatically reboot. Enter your BIOS and reset your first boot device to HDD0 or whatever it was before selecting CDROM. Reboot again and logon to Windows as usual. Select your unsigned theme and enjoy!

If your system won't bootup for some reason, you can bootup into the Recovery Console and restore c:\windows\system32\uxtheme.bak to c:\windows\system32\uxtheme.dll.

This is actually really easy to do, but if you don't have a bootable copy of the Windows XP CD (like if it your system came pre-installed with XP and you only got a 'restore' disk), you probably won't be able to do this. If you don't feel comfortable on the command prompt, you might be better of visiting TGT Soft and grabbing their most excellent Style XP (shareware; $19.95 US to buy) that does all this for you, all with a great interface for installing and managing your unsigned XP Themes.

As always, use these instructions at your own risk. bfarber.com and widescreenxp.com cannot be held responsible if by following these instructions or using the patched uxtheme.dll file, you mess up your system. If anyone knows of an easier way, please let us know.

Enjoy!