computer freezes when playing video

[blah-de-blah]

Why does this happen!! I just reformatted everything, but when i try to play a video in kazaa or using windows media player, the whole computer just slows down (pretty much freezes)...:-\ Does anyone know why?? thanks :?)

[APDesign]

sounds like a ram problem, maybe you are overheating, what are your specs?

[blah-de-blah]

shouldn't be because everything worked fine, its just that i hadta reformat my harddrive, and so i changed from win 2000 to XP. Now i get this problem :-\

[blah-de-blah]

after getting all the critical updates and everything, the same still happens! :( What should i do!!