The SphereXP is a 3D desktop replacement for Microsoft Windows XP. Taking the known concept of three-dimensional desktops to its own level. It offers a new way to organize objects on the desktop such a icons and applications.
I'd highly recommend to try this out, it's so cool. It's still in development, but looks great. It takes some time 'till you figured it out (I lost some of my opened windows, but luckily the Taskbar still resides), but after that it's a very cool experience.
I run this on a PIII 800 MHz, 256 MB RAM and a Geforce3 TI200 GPU-card and it running very smooth, even in the ultrahigh texture modes.