This is really good, and it's a freeware.
I just tried UxStyle Core (
www.uxstyle.com) and it's great, no need to mess with protected system files to use custom themes ('visual styles',
not Windowblinds themes), it installs service process that enables use of unsigned theme files, works on my xp and vista machine, has installer for 32/64 bit.
The only downside is that there are not many good themes, I crawled a lot of web sites and whole DeviantArt and this is the best I could find for myself (Vista Bling Bling by KoKaine golden theme), hopefully you might be more lucky than me:
(SFW screenshot ;P)
