Computer Keeps freezing

Hey guys n gals, hoping you may be able to shed some light on my problem.

My computer keeps freezing randomly, sometimes it may unfreeze and i carry on playing my game but most times it freezes and i have to hold down the power button to turn it off, there is no error and i have no idea what is causing it.

I am on windows 7
2 tb hard drive
GTX 570 GPU
i5 2320 CPU
450 PSU
8GB ram.

I really have no idea why it is freezing and i'm scared it might be damaging my system.

Edit: And i also sometimes get the blue screen of DEATH!!!

Please help!!! :(