No video?

I have this pc that has an onboard video card (ECS K7SEM motherboard). A while back the onboard video stopped working, so an ATI Radeon 7000 AGP card was installed. This too has now stopped working. What I find odd is that there is a BIOS beep and it is booting as normal, but there is no video. Any thoughts? I have tried another video card and have been looking on the net (even the ECS website) but no luck.