You could try reinstalling grub. If you have the first installation disc or dvd you can use that to get into rescue mode and reinstall grub. At the boot prompt, enter
When your Fedora installation has been found and mounted unser /mnt/sysimage, do
Code:
chroot /mnt/sysimage
grub-install /dev/hdX
Change /dev/hdX to the disk where you want grub to be install e.g. /dev/hda for the MBR of the first hard disk.