I think you have to re-install GRUB
boot in rescue mode. here "http://fedoraguide.org/fc2/fc2beginnersguide.html#fc2rescuecdgainroot" is how.
then in the root shell prompt run the command "/sbin/grub-install <location>", where <location> is the location that the GRUB Stage 1 boot loader should be installed.
The following command installs GRUB to the MBR of the master IDE device on the primary IDE bus: