I tried searching for anyone with my issue, but I couldn't find a case of it...so here goes:

Whenever I play a game, or do anything that changes the resolution to fullscreen (including direct x diagonostic tool) I get a "no signal" message on my monitor, and then about 2 mins later my system shuts down.

I have tried (in this order): updating video card drivers, reinstalling directx 9.0c, restoring system to factory settings, replacing video card, reinstalling directx 9.0c again, and updating monitor drivers.

The wierd thing is that I have my system set up in 1280x1024 (60 Hz) resolution and I can get things to run in that mode, but anything else dies....even games in resulutions under this like 640x480 or 1024x768.

I had a Mac Mini hooked up to this monitor until I got my new system last week...and then moved the Mac Mini to a different room (monitor stayed in the same place). The monitor didn't have any problems running in fullscreen mode on that computer (I was running the same exact programs that are causing porblems on my new comp).

Also I can get Elder Scrolls IV: Oblivion to run just fine in full screen on the highest video setting, so I can't see it being a issue with the ram. And like always, Dell insists it is a software issue, and to reinstall the operating system...but I put so much stuff on the computer, I want to avoid losing it all)

Here are my specs:
Dell Insiron 530
2.2 GHz dual processor with 1 GB of RAM and Win XP home
ATI Raedon 2600 XT graphics card
Viewsonic 19" LCD monitor

Any ideas? The guy that came out to install the graphics card said it could be the motherboard, but Dell would rather not replace that if possible.