Ummm... be sure not to stick a AGP card that is 3.3v to that interface. If you do, you will fry it, since it's a 1.5v AGP interface.
Though, it shouldn't fit if it was. What is the video card that you are intending to use?
I guess the other question is.. when it was powered on, with the 1st card you had in it... was it beeping?
And if it was beeping, how many times did it beep, in the interval.
Example: 8 beeps..
beep, beep, beep, beep, beep, beep, beep, beep, pause...
Edit: Doh.. don't tell me that board doesn't have an intergrated speaker.. :roll:
Do you have the PC speaker hooked up? Does the case/tower provide one?
Also Asus does have a voice to tell problems in place of the PC speaker. So you need reg speakers hooked up to the onboard sound card jack.