I've tried everything else and I can't seem to figure this out. I'm currently running a custom built PC, and not until the last 3 or 4 days has it been rebooting randomly. A lot of the time it's while I'm on the internet, but it happens once in a while when I'm running any other program. I've tried testing every component in the system, and everything has test fine without any errors. I've run driver updates, memory tests, CPU tests, mobo tests, USB configurations, and everything else I could possible think of.So I'm trying to figure out if it's a software problem now.

My system specs are:
Windows XP SP2
INTEL 925 Pentium D DUAL CORE 3.0GHz
PCI-EXPRESS ATI RADEON X200 Motherboard
2GB DDR Ram (unsure of the manufacture)
ATI Diamond Viper X1650 Pro Graphics Card w/256MB
160GB SATA Hard Drive

It sounds as though you are getting BSOD's and the pc is restarting.

Go to C:\WINDOWS\Minidump and put 4 or 5 of your latest minidumps into a zip file and attach it to a new reply in this thread, then I will take a look at them for you to see what is causing the crash.

Well, the weird thing is when it does these reboots I'm not getting a BSOD and that's even after turning off the option to reboot on error. On top of that it keeps happening and anything that needs to be kept doesn't save at all. So the minidump only has 2 in it.
Minidump

That's strange, sounds like it's not BSOD's then, but unless you disable the automatic restarts from inside Windows, you need to successfully shut Windows down to save the setting. This is what I've found from experience

This might sound strange to you but I won't look at those dumps because I only download dumps, logs, etc from attachments on the TechSpot server. If there's only 2 files in the Minidump folder then I don't think we'll need them anyway.