I'm really hoping someone could help me out here. I'm stumped and don't know what else to do. Bear with me, because it will be a slightly long read (to explain what I've done so far).
Ok so this problem only started 3 days ago (Thursday 11 February). Prior to this date, I was able to run games perfectly fine. I had not made any changes whatsoever in the system, I didn't install anything.
So I was playing Mass Effect 2 and it crashed. It just froze and I had to hard-reboot the PC cuz it just wouldn't respond. Then it happened again, so I tried different games. I tried Team Fortress 2 (running through Steam) and it crashed a few minutes into the game. I tried Dragon Age and the same thing happened.
So I thought it must be the video card (I'm running Geforce 9800GT). I updated the driver and it didn't fix it. But if you think about it, couldn't have been the driver since I had been playing all my games just fine previously. But anyways...
Oh the form of the crashes is a bit random by the way. Sometimes it locked up the PC. Sometimes I was able to Ctrl+Tab it to switch to a different application (or desktop). Sometimes it responded to the Ctrl+Alt+Del (Task Manager). Sometimes it rebooted itself without me touching anything. Sometimes it would display "nv4_disp display has stopped working normally etc etc" then it messed up the colours.
So I tried to do a system restore (to Wednesday 10 Feb) then I found that on Wednesday there was an installation called "Software Distribution Service 3.0". I wondered if this caused the whole problem. I googled it and found that it is a Windows update. I restored my pc anyway to the 9th Feb point but that didn't help either.
So now I am really confused. What happened and how do I fix this? I read loads of information online and I could see that a number of people have been having the same sort of issues but none could provide a solution.
My PC specs:
OS: Windows XP Pro SP 3
CPU: Intel Core 2 Quad Q8200 @ 2.33GHz
RAM: 4GB RAM (not utilising all 4GB of course since it's a 32-bit system)
Video: Nvidia Geforce 9800GT 512MB, running directX 9.0c
So thanks very very much if you've managed to read up to this point and I'd appreciate any help.