I've had much better luck with XP than Windows 2000. I'm using XP Professional, though Home should be just as reliable.
The best suggestion I can make regarding stability is to make sure you're running up-to-date drivers for all of your hardware, and that you are using the latest (preferably official) version of BIOS for your motherboard. I was having problems with random crashes prior to updating the BIOS on my motherboard, but now those are gone. I have a CUSL2 and am using BIOS verison 1009.
My uptimes average 15+ days, and I do a lot of digital music editing and play an occasional round of UT and Diablo II. My uptime would be longer if it weren't for all the patches that WindowsUpdate throws at me.