FIXMBR Vista
Bootrec
Use the Bootrec.exe (FIXMBR Vista or Windows 7) tool in the Windows Recovery Environment (Windows RE) to troubleshoot
and repair the master boot record (MBR), boot sector, and the Boot Configuration Data (BCD) store. Windows RE can also be used to troubleshoot startup issues. There are two options, Startup Repair and System Recovery Options. Bootrec.exe can be used to troubleshoot additional problems manually.
To run Bootrec.exe utility, you need to start Windows RE. First startup the computer with the Windows install disk. You might need to set the BIOS to boot first from the DVD/CDROM. Select Repair Your Computer and then select the operating system you want to repair. In the System Recovery Options box select Command Prompt and type bootrec.exe and press enter. You can rebuild the BCD by typing bootrec /rebuildbcd to correct startup issues. To correct a corrupted or infected MBR type bootrec.exe /FIXMBR to write a new MBR. Bootrec /fixboot will write a new boot sector to the system partition to correct a damaged boot sector or non-standard boot sector for FIXMBR Vista. If a Windows XP was installed after Vista or 7 you can use this command to restore the Windows Boot Manager by replacing Windows NT Loader (NTLDR).
Master Boot Record (MBR)
MBR is a 512 byte file located in the first sector on the hard drive. It contains partition information and boot code for starting the operating system.
Recovery Console
Recovery console is a utility that can be started from the Windows install CD. You can also install recover console. Once installed you can select it when you first startup you computer. It will be an option on a menu that is presented during the computer startup.
FIXMBR
The FIXMBR is a command used with Recovery Console with Windows XP that writes a new MBR to the first sector of a hard drive. This command is used to fix or correct a corrupted or infected MBR.
The FIXMBR website has some additional articles you might find useful.

you can type FIXMBR at the prompt and the MBR (master boot record) is rebuilt and replaced with a new MBR file. This can usually correct some of the startup problems with a corrupted or infected MBR record. Since the MBR record is the first 512 bytes read on the boot hard drive it is also a target for many viruses. If the MBR gets infected the virus can move into memory and control all other boot processes and disable any anti-virus programs. Most anti-virus programs like AVG will detect and stop viruses, but if you boot the computer to an infect device, such as, a floppy or CD, it can infect the MBR. Just rebooting the computer to Recovery Console and using FIXMBR will remove the virus and correct the problem. One WARNING that should be mentioned is that dual boot systems where you have more than one bootable operating system on a hard drive can be affected so that you lose the ability to boot the alternate operating system. You might want to backup the MBR record first just so you can restore it if needed. I also have a FIXMBR YouTube video you might find helpful.