Why does my PC restart or freeze constantly and what can i do?

[Cavalier]

My homebuilt pc is constantly freezing and restarting on its own when i play games, notably Ragnarok Online ... i recently installed drivers for the Video and Audio and it was working fine but i get home from work and it started freezing and the like all over again. I dont know what to do now... and i dont know why its like this all of a sudden this has been going on for a while now

AMD Athlon 1.8Ghz (reads as 1.15, used to read as 1.5Ghz)
120 Gb Maxtor HD
Integrated Audio and Video by SiS
384 MB SDRAM
Windows XP Home Edition

 

[gibbocool]

It might be too hot. Try to cool it down with a big fan and open the case.

 

[SOcRatEs]

Hello! Welcome to TechSpot

What model MoBo?
With onboard sound/video you may need to look into
fresh bios.
Other than that, try a roll back on the drivers you installed.
I don't trust "system restore" so maybe uninstalling the new drivers,
reboot, then install the previous drivers.
G'Luck