CompTIA A+ Core 2 (220-1202)Software TroubleshootingHard
A technician installed a second operating system on a PC that previously ran Windows only. After installation, the PC no longer boots into Windows and instead shows a boot loader error referencing an unrecognized partition. Which of the following commands should the technician run from the Windows Recovery Environment to repair the master boot record?
- Adiskpart clean
- Bchkdsk /f
- Cbootrec /fixmbr
- Dsfc /scannow
Show answer & explanationAnswer & explanation
Correct answer: C. bootrec /fixmbr
When a second OS installation overwrites or corrupts the master boot record, bootrec /fixmbr writes a new, compatible MBR to the system partition, restoring the ability to boot into Windows.
Why the other options are wrong
- A. diskpart clean would erase the entire disk's partition table, causing data loss.
- B. chkdsk /f repairs file system errors on a volume, not the boot loader.
- D. sfc /scannow repairs corrupted Windows system files, not the boot record.
bootrec /fixmbr
A Windows Recovery Environment command that writes a new master boot record compatible with Windows, commonly used to fix boot issues after installing another OS or bootloader.
- Run from the WinRE command prompt.
- Does not affect the boot sector or BCD directly.
- Often paired with bootrec /fixboot and /rebuildbcd for full repair.
Memory trick: 'Fix the MBR to Bring Windows Back'