I use Microsoft Windows XP Home Edition Service Pack 2, but I have Debian Linux running under coLinux. I actually use the Windows part for very little, short of my games, as well as to recover my coLinux when I get a little too adventurous. Basically, my operating system has become a sort of hybrid, able to run everything. I even have coLinux's home folder as F: via wu-ftpd and Novell Netdrive.
I strongly recommend anyone who wants to try Linux try coLinux. No risk to their main system, no reformatting, not mucking with partitions or bootloaders, no fear of messing the system up from being adventurous, etc. Even for experienced people who need Windows for things, it's a hell of a lot more convenient than dual-booting.
I've had Linux nuts whine to me that it's not real Linux and that that makes it evil. Of course, it IS real Linux, it's just been compiled to run as a Windows APP. I actually use Windows LESS than with a dual-boot because if I, say, need to look something up real quick, I'm not faced with the choice of either having to use a windows-compatible browser and live with the Windows security threats, or reboot every damn time. Windows, despite internally being used heavily, as far as I can see becomes a mere "launcher" for my programs.