Repair the builtin disk defragmenter


The builtin Disk Defragmenter might stop working if having installed a 3rd party defragger and uninstalled it again.

When using the Defrag.exe (XP only) command line tool, then it does not start and one gets the following error message:

Windows cannot connect to the Disk Defragmenter engine.

When opening Properties for a local hard disk, the one either will see a gray Defragment Now-button, or when clicking the button one gets the following error message:

The Disk Defragmenter is not installed on your computer. To install it, double-click the Add or Remove Programs icon in Control Panel, click the Install/Uninstall tab, and then follow the instructions on your screen.

When trying to open the Disk Defragmenter snapin, then one gets the following error message:

Snap-in failed to initialize,
CLSID: {43668E21-2636-11D1-A1CE-0080C88593A5}


To repair the Disk Defragmenter execute the following two commands:

  • regsvr32 dfrgsnap.dll
  • regsvr32 dfrgui.dll

If the above actions didn’t help, then right click the following file and select Install:


Note this issue can also be caused by having disabled the XP SP2 service DCOM Server Process Launcher. This service must be configured to Automatic and be running for the Disk Defragmenter to work.

Note if having disabled or set a low custom size for the pagefile, then defrag might not work. If using WinXP set the virtual memory to “System Managed Size”.

More Info MS KB922379