If you're totally happy with Windows XP and won't be upgrading anytime soon, you're not alone. Just because you don't want to change your OS doesn't mean you're stuck with a boring, 8-year-old desktop.
includes 23 different effects, many of which are "inspired" by those seen in OsX and Compiz. Use it to add visual goddness like kinetic effects and transparency or useful arrangement features like edge snapping and maximizing. There's even a CoverFlow-esque task switcher (invoked via win+tab).
No install is required - just launch the executable and agree to the license. You choose to launch Nimi at startup by placing a check in the white box in the bottom left corner. .Net 2.0 is required.
Some of the effects rendered with a bit of choppiness on my laptop, but it's running Intel GMA and graphical sluggishness is something I'm accustomed to.