Computer freezes (vista)

I have a feeling that I already know what is wrong but I want someone who is more experienced than me to look at this.

Computer specs:
Windows Vista Home Premium (SP1) (clean install)
Manufacturer: Dell
Rating: 4.0 (Graphics)
Processor: Intel Core 2 CPU 6300 @ 1.86 GHz 1.86 GHz
Memory (RAM): 1.00 GB
System type: 32-bit Operating System

Video card:
ATI Radeon HD 2400 Series
http://ati.amd.com/products/Radeonhd2400/specs.html

Before I did a clean install it locked up a lot. (by locking up I mean mouse and keyboard go unresponsive and I am forced to do a hard reboot. All animations that were going at the time [little circle that indicates loading by the mouse] freeze.) At least with a clean install it doesn't lock up so much. BUT

I play a game called KnightOnline (KO for short). It is not a graphic intense game and it is not the prettiest game out there. It is meant for teamwork PvP.

Anyway, a lock up is guaranteed after 30 seconds of being in game.
Event viewer shows only one error. (Unexpected shutdown)
Chkdsk shows no errors.
Memory test shows no errors.

Side note: This PC is at least 3 years old. I'm not sure exactly how old it is. It has had many problems in the past. Many of the problems we have rigged and fixed ourselves but in it's current state, there is no side cover for it with the on/off switch hanging out. (switch problems) We keep air cans handy to keep the dust out. (no moisture gas)

It has no on-board graphics card.

 

It sounds video card related. I would check your temp of your cpu gpu etc.

 

Yea, I'm thinking video card related...

Temperature is probably 50-60 (F) but no more than 70. I don't have anyway to check it. I don't run it long at all before it locks up.

I don't have the pocket book to get another video card :/

 

bump