Actually, there is a much easier way, insert your Mint cd, and follow this guide
http://www.linuxmint.com/wiki/index.php/How_to_repair_your_grub it will restore your grub to what you had before, it will show your old menu, so it will probably way WindowsXP or whatever you had, but if the disk is the same, it will bot Vista, the you can edit your menu.list to say whatever you want.