I see a lot of searches for Grub recovery and Grub help. here are some links if you lose Grub on your system.

The living breathing Grub

Here are some links that will hopefully get your computer going again.

Grub Home Page:  The main source for everything about Grub

PCLinuxoS Forum article: Great article from a real expert!

Distrowatch Weekly 11 January 2010  Grub recovery: Very good source with a fairly comprehensive list of distribution and recovery iso’s to help.

Super Grub recovery disk: Grub recovery software

Linuxhelp.blogspot.com: Good article to get your system working again.

The best recovery is back up important information and files. Sooner or later your hard drive may crash and nothing will help. Secondly, try not to lose Grub in the first place. Install Linux after Windows, not before.

A side note, if you have a system with Lilo, Grub installs well after Lilo, but Lilo generally is not able to write over Grub.