i think i lost my mobo please help!

Hello, tomshardware forums. I've been having some problems with my computer for a while and i could do with some help. Recently my computer started locking up, by which i mean, everything locked up. It would just literally stop. No blue screen of death, no reboot, just stopped. After it was reset, it would sometimes manage to boot, sometimes not get past the POST. Anyway, i did a zero fill of all my internal disk drives and reinstalled windows xp and ubuntu on drive one. For about a day, everything was okay, but now it has started locking up again, sometimes booting, sometimes crashing at BIOS, but never managing more than say, 30 minutes without failing.

Anyway, i don't know what to do. I have an ASUS P5GD1 motherboard, which is about 4 years old. I've been scrambling round the internet, and saw something about removing the CMOS battery and switching the jumper, or something, can anyone tell me exactly how to go about this and whether it is a good idea? If not, is there anything else i can try?

Don't let my flippant use of terms like CMOS and BIOS, or the fact i have linux installed, fool you. I know next to nothing about computers, especially hardware. So please keep this in mind if you are kind enough to reply. Thanks for reading.

Hmmm. Could be, but just before i zero filled, i gave my computer a good blast out with some air and cleaned the fans and stuff, because that was what i thought too. And after i did that, it was okay for about a day, and i was trying out loads of applications running at the same time to see if it would crash. And it was running for a good 24 hours with no problems (i've not had a lot of sleep). Anyway, what else can i do to correct that? The CPU temperature (when i can actually test it) is roughly 69 degrees C or thereabouts. Should i get a new fan or something?