Error codes

0x0000008B

MBR_CHECKSUM_MISMATCH

What it means

The checksum of the master boot record no longer matches what Windows expects, which usually means boot-sector malware or a disk-level change.

Common causes

• Boot-sector malware
• A tool that rewrote the boot sector, such as an old backup or clone program
• A disk with bad sectors in the first track

How to fix it

1. Scan the PC from a rescue USB with a current antivirus before you trust it again.
2. Run bootrec /fixmbr from the recovery Command Prompt to write a clean boot record.
3. Check the drive's health in CrystalDiskInfo. A Caution or Bad status means back up now and replace the drive.