"Class not registered" from explorer, some control panels

[Steven]

Hi,

I can no longer run explorer.exe on my Vista computer. If I type
"explorer" or "C:\" in the run dialog, I get an error message that
says "Class not registered". Also, half my control panels fail to run
with the same "Class not registered" error; the other half run fine.

Can someone please help me fix this without reinstalling Windows? I've
started using a replacement file manager, but I need those control
panels.


POSSIBLE CAUSE?

Several days ago I used a utility called ShellExView to turn off some
shell context menu extensions for zip files. I don't know if this is
when the "Class not registered" problem started or not. I've used this
utility in the past without any problems.


MY ATTEMPTS TO LOCATE/FIX THE PROBLEM

I tried rolling back to a recent system restore point, but that didn't
fix it.

I tried looking in the registry, but my skills are limited. For
instance, one of the control panels that doesn't run is Windows
Update. I tried looking searching for the Windows Update CLSID
(36EEF7DB-88AD-4E81-AD49-0E313F0C35F8). The CLSID is there under
HKEY_CLASSES_ROOT, and the dll mentioned in that entry exists in my
system folder. The CLSID is also listed under "Shell Extensions
\Cached" and "Shell Extensions\Approved", which I guess means it's
kosher with verclsid. It's also there under "explorer\ControlPanel
\NameSpace". Is there some other entry that should be in the registry,
but is missing?

I tried using Process Monitor to look for failed registry reads. There
are many "NAME NOT FOUND"s, but many of them seem to be non-fatal
(i.e., Explorer looks elsewhere or ignores the error). I don't know
which ones are fatal. Here are the Process Monitor traces:

Launching "explorer.exe" from run dialog:
http://www.divshare.com/download/857649-d00 (2695 events, 451KB)

Launching Windows Update from the start menu (expanded control panels
menu):
http://www.divshare.com/download/857730-0f3 (39661 events, 6.7MB)

Both traces zipped:
http://www.divshare.com/download/857762-acf (488KB)


Any suggestions would be much appreciated.

Thanks,
Steven

 

[Steven]

Also, half my control panels fail to run

with the same "Class not registered" error; the other half run fine.

It seems the control panels that *do* work are the ones with .cpl
files in windows\system32. The ones without a .cpl don't work.

-Steven

 

[Don]

Hi,

I can no longer run explorer.exe on my Vista computer. If I type
"explorer" or "C:\" in the run dialog, I get an error message that
says "Class not registered". Also, half my control panels fail to run
with the same "Class not registered" error; the other half run fine.

Do you see the same problem with different user accounts? What if
you create a new user account?

 

[Steven]

Do you see the same problem with different user accounts? What if
you create a new user account?

I only have one user account on this computer. The User Accounts
control panel is broken, so I can't make a new account unless you know
of some other way.

Thanks,
Steven

 

[Don]

I only have one user account on this computer. The User Accounts
control panel is broken, so I can't make a new account unless you know
of some other way.

I just discovered that your broken control panel applets actually run
in an explorer window, which explains why they're broken.

I've been trying to figure out how to use rundll32 to run usercpl.dll,
but no luck so far.

Have you tried booting into safe mode with F8? There is also a 'repair'
function included in the Vista install DVD which I think I might try in
your situation.

 

[Steven]

I fixed it.

I found a system restore point far enough in the past that it fixed
explorer. Messed up some other programs, but I can reinstall/repair
them.

Thanks for all your help, Don.

-Steven

 

[Don]

I fixed it.

I found a system restore point far enough in the past that it fixed
explorer. Messed up some other programs, but I can reinstall/repair
them.

Thanks for all your help, Don.

You're welcome. But a *real* geek would have saved a copy of the bad
registry and compared it to the restored registry and then deduced
what had screwed it up in the first place ;o)