Shell Extensions not working in Windows Vista

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Don Matthews

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Feb 22, 2007, 11:03:32 PM2/22/07

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I have a Windows app that installs two Shell Extensions. The app has
been working perfectly in Win2K and beyond, but the Shell Extensions
do not work in Windows Vista. Anyone know why? I have scanned the
web and have come across the ShellExView utility. It shows that the
Shell Extensions are installed in Windows Vista, just as they are in
Windows XP. I have also come across the information that talks about
the modification to the registry, where you add a DWORD entry
under ...ShellExtensions/Cached that uses the CLSID and is supposed to
tell VERCLSID that this Shell Extension is valid. That did not work
for me, either. The Shell Extensions are indeed installed, they just
are not allowed to run. Everything is installed with an MSI, so I
can't run something at a command prompt with "run elevated".

I am running from an Admin account already, so elevating the privilege
did not seem to have any effect. I also tried the "compatibility with
XP" mode, and no joy there, either.

Here is what I know for sure:

1.) It is not that the Shell Extensions are not installed, they are.
2.) It is not that the Shell Extensions are disabled, they are not.
3.) It is not that my app cannot send commands to the drive I am
controlling due to some problem with the privilege level. I can
successfully send commands to the drive.
4.) It is simply that when I right-click on the drive letter for the
device, in older versions of Windows, my Shell Extension code
executes, and in Windows Vista, it does not.

So I guess I just need to know why the code in my Shell Extension is
not even being called when running in Windows Vista.