A. You can use the Bootrec /scanos command-line tool (part of the Server 2008/Vista recovery environment) to scan all disks on a system and find any missing OSs, then add to the Boot Configuration Data (BCD). Any installations that aren't in the BCD will be displayed, with the option to add them to the boot menu.
If the BCD is corrupt, you can rebuild it from scratch by using the following process. First, back up the BCD information, then set the BCD so that it isn't Hidden, System, or Read-Only. Now, rename the existing BCD, then create a new one.
bcdedit /export c:\bcd_backup
attrib bcd -s -r -h
ren bcd bcd.old