How to Fix BOOTMGR is compressed (Windows Boot Manager)
Quick Answer
The "BOOTMGR is compressed" error indicates that the Windows Boot Manager file, BOOTMGR, or its containing partition has been compressed, preventing the system from booting. The fastest fix often involves using Windows Recovery Environment tools to decompress the boot sector or rebuild boot configuration data.
What Causes This Error
- Accidental compression of the BOOTMGR file or the entire system drive via Windows features.
- Corruption of the Boot Configuration Data (BCD) store.
- Malware or virus infection that modifies boot files.
- Issues with the hard drive or SSD, such as bad sectors.
- Incorrect system shutdown or power loss leading to file system corruption.
- Attempting to install an incompatible operating system or boot loader.
Step-by-Step Fixes
1Decompress BOOTMGR using Command Prompt in Windows Recovery Environment
- Boot your computer from a Windows installation media (USB drive or DVD).
- On the 'Install Windows' screen, select your language, time, and keyboard preferences, then click 'Next'.
- Click 'Repair your computer' in the bottom-left corner.
- Select 'Troubleshoot', then 'Advanced options', and finally 'Command Prompt'.
- In the Command Prompt, type 'bootrec /rebuildbcd' and press Enter. If prompted to add installation to boot list, type 'Y' and press Enter. Then type 'bootrec /fixmbr' and press Enter. Finally, type 'bootrec /fixboot' and press Enter.
- After running these commands, type 'exit' and press Enter, then restart your computer.
2Run Startup Repair from Windows Recovery Environment
- Boot your computer from a Windows installation media (USB drive or DVD).
- On the 'Install Windows' screen, select your language, time, and keyboard preferences, then click 'Next'.
- Click 'Repair your computer' in the bottom-left corner.
- Select 'Troubleshoot', then 'Advanced options', and finally 'Startup Repair'.
- Allow the Startup Repair utility to scan your system for issues and attempt to fix them automatically.
- Once the process completes, restart your computer and check if the error is resolved.
3Check and Repair Disk Errors using CHKDSK
- Boot your computer from a Windows installation media (USB drive or DVD).
- On the 'Install Windows' screen, select your language, time, and keyboard preferences, then click 'Next'.
- Click 'Repair your computer' in the bottom-left corner.
- Select 'Troubleshoot', then 'Advanced options', and finally 'Command Prompt'.
- In the Command Prompt, type 'chkdsk C: /f /r' (replace 'C:' with your actual system drive letter if different) and press Enter. Confirm if prompted to run CHKDSK on next restart.
- Allow the disk check to complete. This process may take a significant amount of time depending on the drive size and number of errors.
- After CHKDSK finishes, type 'exit' and press Enter, then restart your computer.
4Disable Compression for the Boot Partition
- Boot your computer from a Windows installation media (USB drive or DVD).
- On the 'Install Windows' screen, select your language, time, and keyboard preferences, then click 'Next'.
- Click 'Repair your computer' in the bottom-left corner.
- Select 'Troubleshoot', then 'Advanced options', and finally 'Command Prompt'.
- In the Command Prompt, type 'diskpart' and press Enter. Then type 'list volume' and press Enter to identify your boot partition (usually labeled 'System Reserved' or the Windows partition). Note its drive letter (e.g., C: or D:).
- Type 'exit' and press Enter to exit Diskpart. Then, type 'compact /U /S:C:ootmgr' (replace 'C:' with the correct boot partition letter) and press Enter to decompress the BOOTMGR file.
- If the above fails or you suspect the entire partition is compressed, type 'compact /U /S:C:oot' (again, replace 'C:' with the correct boot partition letter) and press Enter. This attempts to decompress the boot folder.
- Type 'exit' and press Enter, then restart your computer.
Frequently Asked Questions
What does 'BOOTMGR is compressed' mean?
This error message indicates that the BOOTMGR (Windows Boot Manager) file, which is essential for starting Windows, or the partition it resides on, has been compressed. When compressed, the system cannot access it to load the operating system, resulting in a boot failure.
How can BOOTMGR become compressed?
BOOTMGR can become compressed accidentally if a user enables file compression on the system drive or specific system files. It can also be a symptom of file system corruption, malware activity, or incorrect system shutdowns that lead to issues with boot files.
Do I need a Windows installation media to fix this error?
Yes, in most cases, a Windows installation USB drive or DVD is required. This media provides access to the Windows Recovery Environment (WinRE), which contains the necessary tools like Command Prompt and Startup Repair to diagnose and fix boot-related issues when the operating system cannot load.
What if I don't have a Windows installation media?
If you do not have a Windows installation media, you will need to create one. You can typically download the Windows Media Creation Tool from Microsoft's official website on another working computer and use it to create a bootable USB drive or DVD.