Hackourlives posted a tutorial about restoring Grub 2.0 after a Windows 7 install

I had Ubuntu 9.10 (this approach would work for 10.04 Lucid as well) already installed on a machine and wanted to dual boot it with Windows 7. Dual booting with Windows 7 already installed is easy as described here. The reverse is not that difficult either.

  Restore Grub 2.0 after Windows 7 Install (Ubuntu 10.04 or 9.10)