The last few weeks have been very frustrating for me, I've been getting a lot of graphics card-related BSOD and random hard lockups multiple times per day. It seems very random, I can lock up while playing games, while browsing the internet, or just a few seconds after windows comes online before I've actually done anything. I can't move the mouse, can't ctrl-alt-del, and the screen just freezes in place, there's no distortion in the display. I don't seem to recall what happens to sounds but I assume sound disappear.

My computer:

AMD Phenom  9550 Quad-core 2.20 GHz
RAM: 4.0 GB
Graphics card: ATI Radeon HD 4800 w/ default settings *not overclocked
Windows Vista: Service Pack 1

Temperatures look fine otherwise. My graphics card floats around 50C and my CPU/HD don't go over 40C

It's your RAM. What make is that shit?

Also thinking it could be RAM. Have you tried researching if there are any compatability issues between your make of RAM and mobo?

Are you aware of how to do a mem test? I would recommend running a mem test at boot so you can identify if the RAM is the problem

Another low-tech idea is to try each piece of ram seperately in case just one of them is bad. Also a good time to check for any dust build up.