From Fedora Project Wiki
Grub2
Starting with Fedora 16, grub2 is used for new installs (upgrades still keep grub1).
Tasks / Common issues
If you have other operating systems setup and wish to boot them via grub2:
# yum install os-prober # grub2-mkconfig -o /boot/grub2/grub.cfg
Setting default entry
1. edit /boot/grub2/grub.cfg, and change the line
set default="0"
to
set default="5"
Other issues
Other grub2 issues: it refuses to install on partition's boot sector (maybe can be forced?) and, !!! this is important !!!, it fails to install if for whatever reason your floppy controller is activated in BIOS and there's no drive connected or floppy disk inserted. The workaround is to run (post OS install) from rescue mode:
grub2-install <target device> --no-floppy
Further Reading
http://www.gnu.org/software/grub/manual/grub.html
http://fedoraproject.org/wiki/Features/Grub2
http://fedoraproject.org/wiki/Anaconda/Features/Grub2Migration