VirtualBox – REGDB_E_CLASSNOTREG Error when Starting under Windows

Once upon a time, I found myself faced to the following error when I tried to start Virtual Box 5 under Windows 8:

Failed to create the VirtualBoxClient COM object.

The application will now terminate.

Callee RC: REGDB_E_CLASSNOTREG (0x80040154)

Starting using the administrator level on the other worked fine and VB started without complaining.

Actually, the issue “suddenly” appeared after I played around with the raw disk accesses feature. During these tests, I re-installed VirtualBox 5 as Administrator.

What common tinkerer like me not always realise is that the Windows Registry also has an access right management, just like files. Right-clicking on a registry folder/group in the Registry editor displays the Autorisations window.

It happened that re-installing as Administrator created the VirtualBox registry keys with an admin level access. As a result, it wasn’t possible anymore to start VirtualBox as non-administrator. Re-installing as “user” did not solve the problem. Likely because some admin-level keys could not be deleted by the de-installation/installation procedure.

The following solution worked for me:

  • Back-up *.VirtualBox* (optional, as all backups usual are ;^)
  • Uninstall VirtualBox
  • Open the Registry Editor regedit.exe as administrator
  • Delete all remaining VirtualBox keys (especially the .NET, driver registrations, Compatibility Manager settings)
  • Re-install VirtualBox using a user account


  • I did not test raising the VirtualBox uninstaller process to administrator level with the sysinternals tools, for instance. That might work as well.
  • The regedit GUI is quite ’90s. Good to know: CTRL+F searches below the currently selected key, which is handy to keep in mind when start searching.
  • I had one key for an USB driver that I wasn’t able to delete due to access rights problems. Finally, this was not needed anyway.

More infos:

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