I will try and make this brief and to the point. My home built system (which has been running smoothly for 2 years now), has just recently experienced some major difficulties. I had been running Windows 7, and put the computer to "sleep." The screen went blank, but the computer continued to run. I then manually shut the computer down. Upon starting the computer back up again, the computer would boot on, but the display would not register an input. So i have no access to BIOS etc. When i turn the computer on, the lights on the front of the computer showing activity, will run for about 15 seconds and go blank. After reseting the CMOS, this problem was fixed and the lights now function as should. But still no display.

Here are a few things i have already tried:
-swapping the VGA card with another one
-removing the RAM and letting it boot on with just one stick
-refreshing the CMOS
-turning the computer on, allowing it to boot for a bit and then unplugging it from the wall to try and force it out of "sleep" mode
-i have tested the monitor with another computer and it works

Other observations:
-occasionally the computer when started will run for 5 seconds and then shutdown, this has been occurring less frequently since the reseting of the CMOS
-the USB mouse and the PS/2 keyboard are not turning on/lighting up like they normally do when the computer is turned on

Here is my setup:
Asus P5QL Pro motherboard
Intel Core 2 Duo E8400
MSI N220GT MD1G graphics card
Asus DVD drive DRW-22b1ST
Wintec RAM 4x1gb
500gb HD
Rosewill Case

Any suggestions would be greatly appreciated! Thanks.