Win XP - PC hangs after 10 minutes of booting

Hi, I have a HP windows XP media center edition. Everything was going great….and then the system froze. Did a hard reboot and then the problem started, now I can't keep the PC running for more than 10min(some times it just hangs right after booting). In safe mode it seems to run a little longer but eventually it'll just hang. When I say the PC hangs this is the behavior - The PC boots..I can launch any application…after a while the application will stop responding, my mouse works, key board works(at least the caps/num key lights toggle), Alt+tab key works and I can switch between applications but the app itself will refuse to respond. If I continue to press the keys or move the mouse around after a few minutes everything will just stop and the internal speaker starts beeping continuously…then I just have to do a hard shutdown of the box I was able to run spybot once and it didn't detect any virus. I am not sure what really is happening. I recently added 2GB of ram and a new personal media drive hard disk. Now I've pulled out the disk still see the same problem. To make sure the RAM is in good condition I ran PC doctor utility and everything seemed fine. This is really driving me crazy…any help will be much appreciated. -Jim

Take a read through this thread and then start a fresh thread in this forum and post accordingly. Please don't forget to include a brief description of your problem, and somebody will be along as soon as.
Helpers look for posts with zero replies which is why you need to start afresh and why i'll lock this one.