Boot from the installation source CD/image.

Enter the Recovery Console by pressing R when prompted.

Enter the number for the appropriate installation.

Enter “bootcfg /list” to list the current configuration.

Enter “boot /rebuild” to rebuild configuration.

At “Enter Load Identifier”, enter the name of the installation (i.e. “Windows XP”.

If prompted for “OS Load Options”, enter “/fastdetect”.

Enter “EXIT” to reboot