Random restarts

Ok so I just put together a new system

Intel 1.8ghz processor
256mb Rambus Ram (RIMM)
Quadro 4 Pro XGL (128mb)
15gb and 40gb sata drives
Windows XP Professional

I know I have a lack of memory, upgrading to 512mb soon (that ram is BLAZING fast even with 256mb) but is that what is causing random reboots? I click into a bout three windows then BAM restarts. Click into Vengeance and BAM restarts. Sometimes I can get into Vengeance and run it fine for as long as I want (usually an hour on Med Settings with 1024res), and can click on a shitload of stuff and listen to music and all will be fine. But most of the time it randomly restarts. Is this a memory problem. Please help me!

That's a "new" system? :p Is all of this equipment brand new? You could try running some burn in software like Prime95; usually can break-in a new system and settle it down. But the most likely culprit would be a shitty/faulty power supply, or bad RAM. Is it a cold boot or warm boot (memory check on POST)? Cold probably PSU, warm most likely RAM.

That's a "new" system? :p Is all of this equipment brand new? You could try running some burn in software like Prime95; usually can break-in a new system and settle it down. But the most likely culprit would be a shitty/faulty power supply, or bad RAM. Is it a cold boot or warm boot (memory check on POST)? Cold probably PSU, warm most likely RAM.

I wish I understood a word you just said. Anyways, I dunno how old the stuff is. The Mobo was used at ATI yet they were getting rid of it (wasnt faulty) so I took it. Other than that I dont think the stuff has been used very much. PSU is fine I believe.