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Windows cannot start new hardware devices because the system hive is too large (exceeds the Registry Size Limit). (Code 49)
http://www.vistaarticles.com/articles/509/1/Windows-cannot-start-new-hardware-devices-because-the-system-hive-is-too-large-%28exceeds-the-Registry-Size-Limit%29.-%28Code-49%29
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Published on 11/16/2007
 
Windows cannot start new hardware devices because the system hive is too large (exceeds the Registry Size Limit). (Code 49)

System hive is too large (exceeds the Registry Size Limit). (Code 49)

To fix this problem, you should first try uninstalling any hardware devices that you are no longer using. If that does not solve the problem, you will have to reinstall Windows.

The system hive has exceeded its maximum size and new devices cannot work until the size is reduced. The system hive is a permanent part of the registry associated with a set of files that contains information related to the configuration of the computer on which the operating system is installed. Configured items include applications, user preferences, devices, and so on. The problem might be specific devices that are no longer attached to the computer but are still listed in the system hive.

The solution is as stated in the Device Manager error code text. To view devices that are no longer attached to the computer, set the environment variable DEVMGR_SHOW_NONPRESENT_DEVICES to 1. Then run Device Manager to view, uninstall, and reinstall these devices.