Way back in 2004 I posted an article talking about the 'The debugger is not properly installed' in Visual Studio 2002/3. Today I wanted to briefly talk about another reason for seeing this problem that an extremely helpful user pointed out (thanks Joel!).

If running debugger diagnostics shows:

Result of 'CoCreateMachineDebugManager(&spMachine)' is '800401f9'

Then you may have bad registry entries under HKEY_CLASSES_ROOT\CLSID\{73b25ffd-f501-437b-8b11-7f0de383964f}. If you have an 'InprocHandler32' key under there, then this is your problem.

To fix it:

  1. Open a command prompt
  2. cd /d "%CommonProgramFiles%\Microsoft Shared\vs7debug"
  3. mdm.exe /unregserver
  4. Open regedit.exe and check if HKEY_CLASSES_ROOT\CLSID\{73b25ffd-f501-437b-8b11-7f0de383964f} still exists. I think it will. If so, delete it.
  5. mdm.exe /regserver
  6. net stop mdm
  7. net start mdm
  8. Relaunch Visual Studio