Can someone PLEASE help as I am on the verge of giving up! I had a pc with specs of athlon 2400xp, 512 333 ram and a gainward Ti4800 graphics card and a cheap L7VTA mobo, all ran no probs at all.... I recently upgraded my motherboard to an xfx NF24-ALH board. PC works fine, except for when I try and play games, its a bit random, but usually when the game loads and the actualy in game graphics appear, or sometimes it'll play until you actually move in the game, the monitor goes blank as if into standy mode as the LED goes from green to amber. I am at a loss as to whats the cause, but with my old mobo it still works fine. I then bought a new grahpics card, xfx geforce 6600 GT and exactly the same thing happens. The new graphics card in my old mobo still works fine! I've checked everything I can think of in bios, AGP 8x or 4x, makes no difference, installed the latest drivers for both mobo and graphics card from nvidia's site...bought a new 450W power supply, no difference, I even formatted my machine to start from scratch (probably a bit pointless) but still the same thing happens.. can anyone please offer any suggestions before I throw in the towel....!

With the information you provided I'd say your new motherboard might have an issue with it. Although it could be a BIOS setting. Turn off write combining and put the AGP Aperture setting at one setting ABOVE you card...for instance, mine is 128MB, so I set it at one above at 256MB. Also, turn off video cache in BIOS and see what happens.

How I would do it in my BIOS (Abit NF7) is to go to failsafe defaults. From there, I would test out the game. Then I would slowly turn up the settings in BIOS, stopping each time to test the game to make sure it is stable. See what you can find and let us know! If the BIOS settings are messing it up, you'll find it. If not, you'll know the mobo is messed...

Sounds like a "compatibility" problem to me. Your monitor goes black (and the LED goes to amber) because something caused loss of the video signal being fed to the monitor. No where in your post do you mention the make/model of the monitor. Have you checked to see if the motherboard is compatible? How old is this monitor?
Your Mfr's website says this motherboard was build specifically for the AMD products and has the NVIDIA nForce2 platform, so your new video card fits the profile OK. I'm not a gamer so I know nothing about the various games except that today's games can be torture to monitors in regards to demanding video. Perhaps with the new video platform (motherboard & card) your game is placing too much demand on your old monitor. With the old system, that motherboard would have been the limiting factor. Something is causing loss of video input to the monitor and it appears to happen when gaming action begins (this is when the most demand is made for response from the monitor). Doublecheck the monitor's maximum resolution and be sure you have set up your system to that and no higher. If you have the latest drivers for the motherboard, video card, and the latest BIOS download, AND you have correctly configured the BIOS settings, I don't know what else to look at. Do you have access to a second monitor perhaps from a friend. You could test your system with that to prove a point. I think I understood you to say the problem only shows up with gaming and action video. Correct?