During a Linux install to my 2nd hard drive, GRUB was automatically installed to the wrong MBR (master boot record). The files were on the /boot of the Linux drive, but the Windows’ drive’s MBR was used. This meant without both drives, I could not boot either operating system.
So I installed GRUB manually with grub-install /dev/sdb. Now I needed to restore the original Windows 7 MBR so that it didn’t require GRUB to boot it.
The Windows 7 “startup repair” from the installation disc detected the OS but didn’t find any boot problems with it, so I went to the command prompt on the disc.
There are several commands for this. A lot of web pages suggest using “bootsect”. However, this did not fix anything. The fact that it was for use on individual partitions was probably a clue on that. Some web pages even used “bootcfg” which is for older Windows installs such as XP (it affects your boot.ini), but is still included on the Windows 7 disc to add to the confusion.
The command that did work was:
bootrec /fixmbr
Afterwards, for good measure, I also ran:
bootrec /fixboot