HTPC image corruption

My HTPC consists of an Intel 1.7Ghz Dothan, on an AOpen i855GMEm-LFS board, with 512mb Corsair, 2x Hauppauge WinTV Nova-T, and a Geforce FX 5200, in a Silverstone LC11 case.

I've been not messing about with it for a while for assorted reasons, and decided to try again with XP on there, to give MediaPortal a good tryout (MythTV's channel configuration is simply nightmarish).

XP installed okay, but on first boot, the image was corrupted - odd colors, screwy, image corruption following mouse, display simply shutting down partway into logon...

Bad, basically.

Smelled like bad GFX RAM, so I bought a replacement card - with 0 improvement.

So... any ideas?

have you tested the Mother board with seperate components.
Had a problem with one of my older PC's where the actual northbridge had given up. sounds bizare yes i know, and is very specific. but i found that i could install windows XP fine and then when trying to boot it, XP would do similar things to what you describe. mine was particular to Random graphics, Random frezzing when loading and such.
i went as far as to turning off on board Intergrated Peripherals only to find the problem continue.

After replacing the mother board EVERYTHING Worked. :D

Have you tried without the AGP riser cards? Have you checked both cards are in properly and that there aren't any broken connections (especially on the small 'booster' card)?

I had some weird problems with a 9800SE AIW and the mobo - it would crash windows in anything but VGA mode (i.e. VGA drivers worked fine, ATI drivers = blue screen at boot). The 9800 is fine in my nForce 2 mobo and the AOpen board is fine with the 9600 I'm using with it at the moment (and was fine with a GF4 4200 too). Things I tried included with and without the riser cards, dropping the AGP speed, a better PSU (run out of the case obviously as I have the same as you) and even a fresh install.

malfunction wins the "we're right" award.

the problem lies with the AGP riser card (though the booster seems fine)

can't get the riser to behave when coupled with: geforce fx 5200 (2 different models), radeon 7000, geforce ti4200, radeon 9500 pro.

which leaves me with multiple options, with varying degrees of success:

* bin the case, get a new case big enough that risers aren't needed (5/5 success chance)
* get a new gfx card, which may cope better (1/5 success chance)
* get a new riser, which may magically work better (3/5 success chance)
* get a new mobo, which may cope better with iffy agp trace lengths (2/5 success chance)

not sure what#s best :/

Surely a new riser is the cheapest option? I'd try that first.