BootRec.exe

For anyone who’s missing the Recovery Console from Windows XP, fear not; it’s still in Windows 7, but in a different form. The new Bootrec.exe command is accessed from Command Prompt in System Recovery Options. This will allow you to perform various actions by adding command line switches.


Repairing the Boot Menu by Using BootRec
The boot menu is the list of operating systems that appears when Windows starts. You will not see this menu if you have only one operating system installed. It can become corrupt, however, and will need to be rebuilt. You can do this by typing bootrec /RebuildBcd into a Command Prompt window.

Sometimes this command won’t work, and you will need to delete the boot menu and rebuild it from scratch. To do this from Command Prompt in System Recovery Options, type the following commands, and Windows will rebuild and restore the boot menu.

Bcdedit /export c:BCD_Backup
c:
cd boot
attrib bcd –s –h –r
ren c:\boot\bcd bcd.old
bootrec /RebuildBcd

There are other useful switches for use with the BootRec command.

/FixMbr
This switch, used at bootrec /fixmbr, will repair the master boot record (MBR) in Windows 7.

/FixBoot
This option, used at bootrec /fixboot, will write a new boot sector to the system disk. This can be useful if the boot sector has become corrupt or damaged, perhaps by trying to install an earlier version of Windows on the disk.

/ScanOS
This option, used at bootrec /scanos, will scan your hard disks for any compatible operating systems that may not be viewable on the boot menu.

BCDEdit
This is a program used for maintaining, changing, and rebuilding the boot menu in Windows 7. You should not need to use BCDEdit to repair your copy of Windows 7, because the tools I have mentioned already should repair any problems. However, if you need to use this tool, you can find detailed instructions on the Microsoft support website at http://technet.microsoft.com/en-us/library/cc709667(WS.10).aspx.

When you are finished with Command Prompt in System Recovery Options, type exit to close the window.

Source of Information :  Microsoft Press - Troubleshooting Windows 7 Inside Out