Is it RAM or the GPU Causing The Issue?

I'm trying to fix my girlfriend's Dell computer, and it's boggling my mind. Normally I'm pretty good at troubleshooting, but this is just odd.

She has a Dell Inspiron 530, it's about 3 years old.

- 6GB DDR2 Hynix RAM
- ATI Radeon 2600XT HD
- Intel Q6600 Quad-Core

The problem started about a month ago. Randomly the computer will do one of two things:

1. It will completely lock up. I can't move the mouse, do anything. I have to manually press and hold the button. It doesn't matter if I'm gaming or browsing the Internet.

2. The screen will go black, and the monitor enters "Power Save" mode. However, if music or anything is playing, you can still hear it and anything else running. So it's like the video card just gives out.

I have ran Memtest overnight, it came back with no errors after about 6 passes. So that just makes me think it's the video card.

I have updated the drivers to the card, updated Windows, defragged, etc. Nothing is helping.

Can anyone help me with this frustrating issue? Thanks.

You using the dell power supply? Those rarely go above 305 watts. I would see if yours has any special leads and get it replaced. Like the motherboards, they just get the job done, and may not last.

You're correct about the 2600xt; I have one for testing only (I normally use onboard video). Only other item is possibly the cpu getting warm. Some dells use a fanless heatsink with plastic cowl using the back fan to draw warm air away from the cpu. If the cpu heatsink is removable, you might clean it and apply some good thermal grease such as arctic silver. But I could be wrong; the ps may also be overheating. I use a special solvent spray to clean the case and ps fans at least once a year. It's only about $3-5 per can or two for $5 on sale. It's much safer than wiping anything with a cloth.