I am not sure about Fedora, but judging from my SuSE Distro...
Let Linux reinstall itself, on the SuSE install there is an option to fix the existing INSTALL, meaning that it will reinstall GRUB and set the appropriate settings...
alternatively you should've had a BOOT Diskette (backup) handy...
Ben
"If it works don't fix it! If it doesn't use a sledgehammer..."