Mobo not recognizing video card

Here is my computer:

Therm PSU 550W
ASUS P5K-vm mobo
Intel Dual Core 2.2 g cpu
2 gigs ram
XFX 8600 GT video card
Linksys wireless card

Had this system for over a year and half, then all the sudden no output through monitor. Powered everything down, opened case, the powered back up. All fans, lights and everything else is working. Still no output. Switched monitor to onboard vga and presto, screen appeared. So I switched video cards, tried again, same problem. Was adviced PCI-E slot could be bad. Tried a different mobo with both old and new video cards, same problem. Tried different ram in both mobo, same thing. Checked PSU, good to go there. The only thing I haven't swapped is the CPU, can this be the problem? Also Used two different PSUs.

"Tried a different mobo with both old and new video cards"

What do you mean by that?


I dont understand what you mean by old and new video cards.

My friend's having an almost identical problem. However, one of his monitor's itself turned out to be faulty. Now another of his monitor's again shows no output at times. After switching to the onboard VGA, the display appeared. But now it's going off randomly. At times it'll work with the graphics card; at times with the onboard VGA. And sometimes not at all. I thought it could be a faulty mobo. But now since you say you've changed motherboards and still get the same problem I'm really confused.

Was just wondering, though it's highly unlikely, could both the video cards you tested be bad?