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Device Manager code Code 49: Windows cannot start new hardware devices (system hive too large)

Updated

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What the code means

"Windows cannot start new hardware devices because the system hive is too large (exceeds the Registry Size Limit). (Code 49)" (Code 49 - CM_PROB_REGISTRY_TOO_LARGE)

Code facts for Code 49

Code as Windows shows itCode 49
TypeDevice Manager code
Symbolic nameCM_PROB_REGISTRY_TOO_LARGE
Hexadecimal, 8 digits0x31
Decimal (unsigned)49
Decimal (signed 32-bit)49
GroupDevice Manager and device errors

Read with care

  • Device Manager codes are decimal problem numbers (CM_PROB values), not Win32 or HRESULT codes. Win32 error 49 is not even defined in the System Error Codes list. (Device Manager Error Messages)

Code facts: Code 49 - CM_PROB_REGISTRY_TOO_LARGE (Microsoft Learn, CC BY 4.0), checked Nov 14, 2026.

Code facts: Device Manager Error Messages (Microsoft Learn, CC BY 4.0), checked Nov 14, 2026.

Where this error shows up

This code shows up in Device Manager, in the status box of a device that has a problem, or in an app that cannot use a device (such as the Camera app).

Applies to

Windows 11 and Windows 10 (as listed at the top of Microsoft's Device Manager page)

3 steps to try, in order

Steps are grouped by the Microsoft page they come from. The page lists only what those pages give; other causes of Code 49 are not covered. 3 steps are flagged.

If this page and Microsoft's page differ, follow Microsoft's page.

From: Error codes in Device Manager in Windows

Source: Error codes in Device Manager in Windows (Microsoft Support), checked Nov 14, 2026. Summary in our own words; Microsoft's page has the full steps.

  1. Remove devices you no longer use

    Disables or removes drivers

    Make Device Manager show disconnected devices: open the Run box (Start > Run), type cmd to open Command Prompt, then type set devmgr_show_nonpresent_devices=1 and press Enter.

    In Device Manager, choose View > Show hidden devices; devices that are not connected now appear in the list.

    Select a device that isn't present, and on its Driver tab choose Uninstall. Repeat for every non-present device you no longer use, then restart the PC.

    Open the device's Properties in Device Manager again to see whether the error is gone.

    Microsoft advises: Save your work and close all apps first. If Windows doesn't reinstall the driver after the restart, update the driver from Device Manager. (Update drivers through Device Manager in Windows)

From: Code 49 - CM_PROB_REGISTRY_TOO_LARGE

Source: Code 49 - CM_PROB_REGISTRY_TOO_LARGE (Microsoft Learn), checked Nov 14, 2026. © Microsoft, licensed under CC BY 4.0. Steps shortened and reworded by PC Driver Update.

Microsoft's driver documentation page for this problem code (written for driver developers); only its recommended resolution is used.

  1. Remove non-present devices

    Disables or removes drivers

    Set the environment variable DEVMGR_SHOW_NONPRESENT_DEVICES to 1. This causes Device Manager to display installed devices that are currently not present. Use Device Manager to remove these devices.

    Microsoft advises: Save your work and close all apps first. If Windows doesn't reinstall the driver after the restart, update the driver from Device Manager. (Update drivers through Device Manager in Windows)

  2. If the registry is still too large

    Resets or reinstalls Windows

    If the registry is still too large, reinstall Windows.

    Microsoft advises: A reset or reinstall can remove your apps, settings and personal files, and a clean install removes everything on the drive. Back up your important files first, and if BitLocker is on, have your BitLocker recovery key ready. (Recovery options in Windows)

Stop and get help

If these steps do not fix the problem, or you are not sure about a step, stop and get help from Microsoft Support or from the maker of your PC. Stop at once if the data on this computer is at risk: back up your files first, or ask a professional before you go on.

Dates and review

Automated checksfirst check: ; fourth check:
Microsoft pages read
  • Error codes in Device Manager in Windows: read , the Microsoft page is dated Mar 31, 2026
  • Code 49 - CM_PROB_REGISTRY_TOO_LARGE: read , the Microsoft page is dated Mar 3, 2023
  • Device Manager Error Messages: read , the Microsoft page is dated Mar 4, 2020
Review statusCleared for publishing after the automated checks on .