Try as root;
Code:
rpm -Uvh http://ftp.freshrpms.net/pub/freshrpms/fedora/linux/6/freshrpms-release/freshrpms-release-1.1-1.fc.noarch.rpm
When done as type something like;
yum clean all
yum -y install ati-x11-drv
After the package(s) are downloaded and installed still as root try one of the following;
Xorg -configure
system-config-display --reconfig
Test by using the is suggested by the Xorg command or by typing 'startx' minus the single quotemarks if you used the system-config-display command.