Out of Range in 3d accelerated games

Good afternoon,
I was wondering if anyone could help me out with this issue. Ive been trying to solve it on and off for years now.

Basically, I have a custom built desktop that apperantly keeps losing connection with graphics card or something. When playing a game like Serious Sam, Myst 5, or Sims 3 the monitor will eventually (and at random moments) go black and more often then not display the {OUT OF FREQUENCY} message.

Now sometimes ill be able to Alt-Tab to the desktop when this happens, but I cant start any game until ive rebooted again.
I know its an issue with the graphics card because I had an older graphics card before that ran Serious Sam just fine and never went out of range.
I replaced the card so that I could play F.E.A.R. and ever since ive been getting these errors. Id put the old one back in but It was given to my brother a couple years back.

The desktops running on Windows Xp with a Radeon 9550/x1050 series card. I dont think its overheating cause I replaced the powersupply to a 450watt and the only other peripherals are the CD drive and the floppy drive. Ive tried replacing monitors from a 17 inch tube monitor to a 22' lcd and that didnt work (even with monitor drivers installed)

Ive uninstalled the graphics drivers before trying out the following drivers (seperately of course) the drivers that came on disk with the card, the latest drivers from the amd website and some previous versions, and omega third party drivers. Despite many driver changes nothing worked.
Lowering the resolution and changing the refresh rate did nothing for me. I even tried setting the resolution and refresh rate in game on sims 3 to the exact res. and refr. rate that i had the desktop set at. The computer has also been reformated and Windows xp reinstalled. Still have the same issue.

Im leaning to the conclusion the the card I bought was bad from the start. But id hate to believe it.

I checked the other threads with similiar issues but the stuff suggested there ive already tried to no avail.
Thanks again for any help you guys might be able to offer. Ill reply with instant feedback on your suggestions.