How do I recover from a GRUB 21 error.

When I finshed the install and re-booted, at the end of the boot session, I received an Grub error 21. Checking some of the docs, it seems that this means that GRUB cannot find the boot location. First, is there a way to fix this problem by editing a configuration? If that fails, is ther a way to remove Ubuntu and try to re-install it from an external drive? Is there a simple text editor that I may use to modify any coonfiguration file to fix this problem? During the Ubuntu installation, the install notified me that "There were no users or operating systems suitable for importing from." I continued the installation

The install completed, but I can only boot the computer using the Ubuntu disk. It will not boot from the hard disk. I checked the file system and the operating systems seem to be intact, the problem seems that GRUB is not loading and allowing the computer to boot.

Any help is appreciated.