Fedora Core 9 Video Driver Issue

Hi,

I recently installed Fedora Core 9, and when i finished updating, i changed the driver from the generic vesa display package, to an ati display package. I have a ATI Radeon 4850. The package claim it had current radeon drivers, and said that i would need to restart the X server. When i restarted it would not load up in a gui mode, and brought me to the terminal login window, i logged in under root, and used the display command, and it said that X server could not be found. Is there a command i can use in the terminal inferface to reset/change the display package back to a generic one, so i can re-enter fedora in a GUI mode. Thank You.