How to fix “BOOTMGR is compressed” (Windows 7/8/10/11)

Seeing “BOOTMGR is compressed. Press Ctrl+Alt+Del to restart” means Windows can’t load the Boot Manager file it needs to start. The PC typically gets stuck in a reboot loop and won’t reach the Windows login screen.

Why this happens

• Drive compression was enabled on the system/boot partition (often to “save disk space”).
• “Compress this drive to save disk space” was turned on for the C: drive or a boot partition.
• Boot records are damaged (MBR/boot sector/BCD) after a failed update, disk error, cloning, or power loss.

Before you start

• If your disk is making unusual noises or SMART reports errors, clone it first (a failing drive can get worse during repairs).
• If BitLocker is enabled, you may be asked for the recovery key when accessing the drive in recovery tools.

Solution 1: Fix it with Windows installation / recovery media

This method works for Windows 7, Windows 8/8.1, Windows 10 and Windows 11.

1. Boot the PC from a Windows installation DVD/USB, or a Windows recovery drive.
2. Choose your language and keyboard layout.
3. Open the recovery tools:
   • Windows 7: click Repair your computer.
   • Windows 8/10/11: click Repair your computer → Troubleshoot → Advanced options → Command Prompt.
4. At the Command Prompt, identify the Windows drive letter (it may not be C: in WinRE):

   diskpart
   list vol
   exit

5. Uncompress the system drive (replace C: with the correct letter you found above):

   compact /u /a /s:C:\

   This uncompresses files and folders on the drive. It can take a while on large systems.

6. Restart the PC. If Windows still won’t boot, go back to Command Prompt and run the boot repair commands below.

Repair the boot records (if uncompressing alone didn’t solve it)

1. Return to Command Prompt from the recovery tools.
2. Run these commands (they do not require a drive letter):

bootrec /fixmbr
bootrec /fixboot
bootrec /rebuildbcd

If bootrec /fixboot returns “Access is denied” (common on some Windows 10/11 setups), try:

bootsect /nt60 sys
bootrec /fixboot

Still not booting? You can rebuild boot files using bcdboot (replace C:\Windows with the correct Windows folder path and S: with the EFI/System partition letter):

bcdboot C:\Windows /s S: /f ALL

Solution 2: Fix it using Lazesoft Recovery Suite Home Edition (freeware)

If you don’t have Windows installation media, or you prefer a guided tool-based approach, you can use Lazesoft Recovery Suite Home Edition to uncompress the partition and repair boot problems.

1. On a working PC, download and install Lazesoft Recovery Suite Home Edition.
2. Create a bootable recovery USB or CD/DVD.
3. Boot the problem PC from the Lazesoft recovery media.
4. On the Lazesoft home page, click Load Drivers (if your disk is not detected, load storage/RAID/NVMe drivers).
5. Open the drive/partition browser and uncompress the Windows system partition from the partition Properties window (this reverses the drive compression that triggers the error).
6. Run the boot repair tools as needed:
   • Boot Crash → MBR Repair
   • Boot Crash → Fix Boot Sector
   • Boot Crash → Missing Windows File Repair (repairs missing/corrupted boot files)
7. Reboot the PC. The “BOOTMGR is compressed” error should be resolved.

Quick FAQ

Can I fix this without losing data?

In most cases, yes. The steps above focus on uncompressing boot files and repairing boot configuration—your personal files typically remain intact.

What if my drive letter is not C: in the recovery console?

That’s normal in WinRE/WinPE. Use diskpart → list vol to find the correct Windows volume, then use that letter in the compact command.

What if Windows still doesn’t boot?

If you still can’t boot after uncompressing and repairing boot records, the issue may be deeper (file system corruption, failing disk, or a damaged Windows installation). At that point, back up important data (Lazesoft can help) and consider running a Startup Repair or reinstalling Windows.

If you need help, please don’t hesitate to contact Lazesoft support.