Aren't you the one who typically answers MY tech questions???
More importantly, what's a new system doing with AGP?
Naw, nothing wrong with that. Anyway, in my experience, computers like to grey things out when they don't think they can accomplish said task...I know mine occaisionally likes to deny that my monitor is capable of 1280 by 1024 resolution...I got around that by doing a system restore...
Your problem, though, sounds like a bad hardware-detection issue...which makes me think of drivers. I'm sure you've tried a lot of them, when you say you've tried "many different drivers," but there may still be something else. I'll look around a bit on their website and post again if I see anything.