When you installed Win 7, it replaced grub in the MBR (master boot record) of /dev/sda with the windows bootloader.
To repair your grub, boot the Linux installation CD of Fedora 11. It should offer the option to boot from the hard drive. Select that option and it will find Fedora on the hard drive and boot it. When Fedora is running, run the grub-install /dev/sda command to repair grub in the MBR.
Then you will have to edit /boot/grub/grub.conf to and a menu entry for Win 7.