How to Fix My Freezing Toshiba Satelite C655-S5049?

I have been working on this computer for a month already and I have not gotten anywhere. I DESPERATELY need help.

Every 10 to 30 minutes it freezes. It happens while I'm watching videos, YouTube or Computer. And then sometimes it does it when I'm just surfing the web. My browser is Firefox. It used to do this at this one shop, and when I got home it stopped. Now it's at home too, after I moved. One time it wasn't even lagging and it just froze. Some times I have to restart with the power button sometimes I just have to wait 4-10 minutes. It's been doing this since August or so.

I have already got drivers, virus scan, installed windows like 4 times from the USB, defrag, disk error registry clean, got new 2GB ram (it had 2GB at first, so I'm not going over it) and I was GOING to try system factory reset, but every time I try to the warning sign does not appear so I can't do that either.

Please please please, help.

Additonal Information: I have a Windows 7 62 bit and I have already system restored from points