CoD2 freezing issue

Not sure how and where to start about this but here i go.

Around a week ago i was playing in CoD2 when my pc just froze on me. I could not hear anyone on my headset, the game picture was just like me taking a screen shot. Well i turned the pc off and back on again and it was fine. Went a few days and it did it again. I checked in my event viewer to see if i had any error messages, there was not any.

Now since Monday, my pc crashes every time i play a game.

Could this be down to my graphics card over heating? or can there be another explaination for this.

Graphics card i have is Radeon X800GT about a year old.

Can anyone help?