I am getting this error when attempting to preview local sites (I have been
documentation for the past few weeks, so it is likely something that I added
in that timeframe).

Message in Event Viewer:
--------------------------

aspnet_wp.exe could not be started. The error code for the failure is
C0000022. This error can be caused when the worker process account has
insufficient rights to read the .NET Framework files. Please ensure that the
.NET Framework is correctly installed and that the ACLs on the installation
directory allow access to the configured account.
For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp.

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Message in browser
-----------------------
Server Application Unavailable
The web application you are attempting to access on this web server is
currently unavailable.  Please hit the "Refresh" button in your web browser
to retry your request.

Administrator Note: An error message detailing the cause of this specific
request failure can be found in the application event log of the web server.
Please review this log entry to discover what caused this error to occur.

---------------------

Things I have tried already
==================
1. Checked machine.config
2. Checked IIS to make sure running 2.0.50727
3. Ran aspnet_regiis -ga against the ASPNET account on the machine
4. Cleared the Temporary ASP.NET Files folder
5. Explicitly granted ASP.NET account access to the entire Framework folder

6. Finally uninstalled KB939373, an IIS patched
released last week, as it is the most likely culprit for my pain. Nada! Back
to drawing board.

7. Also tried altering the account ASPNET uses in machine.config. Still
nada.
8. Temporarily made ASPNET an administrator. NADA

Guess it is down to either reinstall of .NET or toast the machine. Woo
Hoo!!!