Adding AGP card to replace onboard gfx

Hi, I had a spare 9800pro AGP card that I gave to my sister to upgrade from an onboard gfx setup. I installed the card and hooked up the monitor and installed the latest drivers and everything ran fine.
After a while though things went wrong and now I can only get a display on the monitor when plugging in to the vga socket on the mainboard and removing the 9800pro.
I am not sure what I am doing wrong, had a good look through the bios and couldn't find a setting to disable onboard gfx, only a selection to change the 1st display device to AGP.
I'm unsure what the board is but it uses a Phoenix bios.
The system is a 2.8ghz Pentium 4 with 1gb ram. Anyone have any tips ?
Thanks.

There should definitely be an option to turn off the onboard GFX in the bios somewhere, check carefully.

Try removing the old onboard drivers from Windows too... probably easiest to do it in safe mode.

Edit: Try resetting the CMOS too. (Before anyone says it won't help, it has helped me many times! :mad:)

Is there a jumper on the board for onbaord off/on. The type of motherboard you have would also help

I'll have another look in the bios but I am pretty sure I couldn't find any settings. A jumper seting is possible, I'll try and find the model number of the mainboard.
Thanks for the replies.

The board is based on a Radeon 9100 onbard grpahics, but I have been unable to check the manufacturer as yet.

Any AGP speed setting? This is important since different speeds supply different voltages.

Hi

Some MoBo's automatically switch off on-board gfx when a card is plugged into the PCIE/AGP slot.

The fact it was working, and now doesn't when the 9800 is plaugged in, and removing it means the on-board works OK - suggestes either a blown 9800 or blown AGP slot. Any way you can check the 9800 on another compter, or a different AGP card on that computer? Will probably tell you whats going on....

Thanks again for the replies. My next step will be to try it in another system, after speaking to my sister the 9800pro was working fine, then whilst playing a game she altered her monitors brightness setting and then the display just went.

Could it be a LCD setting for VGA/DVI that was accidently hit when going for brightness?

No, it's an old 17" crt mate.

Have you got another agp card you could try in the same socket? If that doesn't work it would suggest that the socket has gone :(

I brought the card back and tried it in an old system and it didn't bring up a display so I think maybe the card is dead.
Anyone know what a reasonable AGP replacement would be, which could still perform at an acceptable level in games ?
Thanks.

Brand new OEM X800Pro for £104.43 inc VAT?