Compaq Evo N610c freezing.

Hey everyone. Im new to the forum so a big hello first!
Now for my question.
Ive got a Compaq Evo N610c. It came with Windows 2000 installed on it.
Awhile back I upgraded to Windows XP, but Im using the student edition.
Around the same time, I got into gaming.
It seems like I will get 10-15 minutes into a game and my computer will just freeze and Ill have to reboot.
Im not sure if this is a computer issue or an OS issue.
But once I reboot, no matter what I do (internet surf, back to game) it freezes again. Its a continuous thing.
Its getting to the point where Ill use my computer for about 20 minutes and then its just too much of a hassle.
Can this be an OS issue or is this a computer issue?
Has anyone had this problem?
Im no longer covered under warranty.

 

Is it getting hot? Perhaps a cooler might help. Also clean the vents to ensure that air is passing through.

 

well u did not say your computer specs but im guessing u need more ram