A friend of mine has a pretty old custom-built computer that has recently been experience graphical glitches that have now escalated to the stage where it has become unusable and he's asked me to take a look.
The problems are apparent even at BIOS stage so I've ruled out any software / driver issue (although if I'm wrong to rule those out please tell me!). There are random colours shifting across the screen and some of the letters are missing or have been replaced with strange symbols. This happens when I connect his graphics card to my monitor using both the VGA and DVI connectors. From time to time (normally after I've removed the card and from the AGP slot and re-seated it) it will work fine, but only for a maximum of two reboots before it goes again. Often, the screen just stays completely blank after POST. When I remove the card and connect the pc up using the standard vga connector on the motherboard it boots perfectly.
So I'm pretty sure it's one of three things. The graphics card is failing/failed, the AGP slot is faulty, or maybe the PSU is failing and the extra draw from a dedicated graphics card is tipping it over the edge. I don't have another AGP card to test in the slot without buying one, or another motherboard with an AGP slot to test the card. Does anyone out there know of any way of finding out which is the problem without purchasing a new card? Reluctant to do so in case it's a motherboard issue but obviously I will if I have to.