stop right there for a sec. lets talk about this...
you say no beep, no post?
are you sure there was no post... could there have been a post, but you didn't see it b/c there were no drivers installed at that point? and/or the on board was still active and monitor was connected to the new vid. card...
None of that is possible man. When the computer is posting and in the BIOS the card doesn't use any drivers to display what you see on the screen. If it posts it beeps which he said it didn't. If it was the card it'd also not beep.
The only way you can 'not see' the post is simply by having the cable unplugged or looking away....it doesn't show up in the background because there's no drivers....theres no drivers to install for the BIOS and POST to be displayed...it's all in windows
As far as the onboard goes, again like I said since there's no drivers, it shouldn't have had a conflict. He puts the new card in, plugs in monitor, go into the BIOS and disable onboard and should be done with it.
The only way to test if it's CPU or mobo is with a PCI Post card (and beedub said you'd never use one
) but yeah it's not worth going out and buying one simply for that...was just letting you know that's about the only way unless you have a spare CPU you can throw in the board and if it boots up then it looks like it's your current CPU.
This is going to be rather simplistic but did you try resetting the CMOS to see if for whatever reason something in the BIOS got changed that it wasn't supposed to..
Clearing the CMOS will reset the BIOS to it's defaults and perhaps that'll sort out your problem.