Atbow is a nice program that automatically changes your wallpaper for you. You can set the time interval, specify folder to choose images from, and choose shuffle / in sequence etc.

http://www.dxcoder.org/altbow/en/index.htm

I use it with a folder i have of 1200+ 1920x1080 images, and set it to change every hour. Never a dull moment on my desktop...!

1) You need to download the directx update like it says
2) Have tested in both xp 32 and vista 64
3) Tell people about it, still hard to find even on google