theres a whole pinned article about random reboots.
the problem could be lying within the ram, mobo, psu, cpu, overheating, many many things.
i had the same problem though, replaced my ram with some patriot ram and it was good as new. you could have some bad sectors in your ram like i did. i only have a 420 watt and i run
heatsink on my cpu
5 case fans
creative audigy platinum sound card plus face attachment
1 gb ram overclocked
radeon 9600 video card
56k modem pci
wireless antenna pci
1 10k rpm raptor hdd
1 maxtor 160 gb hdd
i think im pushing my psu's capabilities. theres an excellent psu for sale at newegg, one day sale only. its the antec 500watt one, its on the front page of newegg right now for 50 bucks, 300 possitive reviews.