I suspect the problem is your video card and drivers. There are some possible solutions, but first let me ask:
What OS were you running before trying to install Win 7 RC? Was it XP? Was it Vista?
Which Win 7 RC version are you trying to install? Is it 32-bit or 64-bit? Did you download it from MS?
The reason I am asking is that if you were running Vista before, then you can use DriveMax (a free program) to transfer your video driver files over to Win 7 RC. If not, then we will have to look for other possibilities.
For example, do you have access to another 8X AGP card with more recent drivers? FX5200 might have to be updated for the more intense graphics available now, especially Aero.
Just some thoughts ... hope they help.