Hello! See if the radeon driver is blacklisted.grep radeon /etc/modprobe.d/*
If yes, you could try unblacklisting it. (Put a # in front of the blacklist radeon line in the file where it is to comment it out. Leave the radeonfb entry blacklisted if it is.) Need super user rights to edit stuff under /etc/. Then reboot.
Since it's an older ATI this could work. This might however also make your system not boot at all so better have a live media close by!
Good luck!
