How to hack Windows themes:

Step 1: Download uxtheme.zip and extract it somewhere on the hard drive.  (I assume you will extract it to c:\ because that makes it really easy.)
 

Step 2: Restart Windows into DOS mode and replace c:\Windows\System32\uxtheme.dll with the one in the zip file. (you may want to back it up, just in case)

Step 3:Find some cool theme on Themexp.org and download that file to a new folder in C:\windows\resources\.  Then right click the desktop, choose 'properties', goto the 'Appearance'  tab and select the new one.  This should work...see Themexp for specific help.