I usually buy a new home PC every couple of years. At least that's been my track record since college. My current desktop is a Pentium III 600MHz that I bought in November of '99. So I'm a little overdue at this point.
But right now, I don't have a real need to buy a new PC. 600MHz still runs all my games and applications pretty well. I've maxed out the RAM on the thing (768MB) since RAM has gotten so cheap. I've got tons of disk space (around 90GB total). So, I think I'm going to hold off a little longer this time. Maybe I'll wait for the 3GHz chips to appear here.
The same goes for Windows XP. Windows 2000 does everything I need. It's very stable-- I only reboot when I have to install new drivers or something like that. I don't care to spend $199 on an upgrade that is giving me little more than cosmetic changes.
What are your upgrade plans for this year?