Dell Studio with Vista Freezes

My desktop recently started freezing for no apparent reason that I know of. The screen will just lock up and I have to restart with the power button. That doesn't always work either and sometimes I cant even boot into safe mode. I have not added any new hardware in 3 years but there is a new icon in the bottom right tray that says "Safely Remove Hardware". This has just recently appeared within the last few weeks. The only thing we use it for is web surfing and my son plays Minecraft on it. I think there may be a good possibility that maybe he did something or downloaded something bad for his game.
There have been bsod's 1 or 2 times and if I remember right, maybe something about memory dump.
Please help. Scared something major might have happened.
Thanks
Flatfoot1121