Even if Fedora setup discs don't have the "repair" option mentioned, you can use any Linux LiveCD around to boot up, mount and chroot your Fedora installation and reinstall GRUB from there. It's easier if Fedora offers an "automated" way for this, though.
You can install Windows (any version, really) on the disk, but if you want to get out of that the easiest (though not necessarily the shortest in time) way, consider taking backups of your data (mainly /home I guess), creating completely new partition layout to the disk (Windows partition the first primary partition, rest for Fedora), installing Windows to it's partition first and Fedora over the rest of the disk after that. That way you'll get the partition layout correct for Windows, you'll get GRUB configured the right way automatically and don't have to mess up with moving or resizing partitions and doing odd stuff like that. It's a question of personal taste, and if you're ok with doing some manual configuration, you'll get the installation faster done if you don't reinstall both OS' but just arrange some space for Windows and deal with GRUB reinstallation after Windows is there.