My HP G62 computer keeps freezing up!?

after being inactive for about 10-15 mins. Sometimes it doesnt freeze up but more often than not it does. I can not do anything on the computer when it freezes. The only way to unlock it is to press and hold the power button. I have scanned it for viruses using norton 360 and even used the power eraser option on their site. So I dont think that a virus is the issue. HP is useless and wasted 2 hours of talk time for me. the computer is 3 months old and the fan is working so I dont think it is getting too hot. HELP I NEED this computer.