Heck, I'm still running Win98SE. With good hardware and good drivers it can be very stable, and with current hardware, it's VERY fast. The only reason I'm running a Microsoft OS at all is that I (unfortunately) develop MS Access based software (puts food on the table and pays for my technology habit). Otherwise, I'd be using some flavor of Linux.

Obviously, that's not an option in most corportate IT environments run on M$ domains, but it works for me.