Vista - ASP.NET MVC (Un)Installation Issue

I'm not really sure which newsgroup best fit this question, so I
apologize ahead of time if this message is off-topic.

About a month ago, I started getting into ASP.NET MVC with Preview 4.
Yesterday, I uninstalled Preview 4 and installed Preview 5. Upon doing
so, I ran into an issue with running both new and existing MVC projects.
Immediately upon running the application, the following exception is
thrown:

Could not load type 'System.Web.Routing.StopRoutingHandler' from
assembly 'System.Web.Routing, Version=3.5.0.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35'.

I had already updated the project references from the Preview 4
assemblies to the Preview 5 assemblies, so I checked the GAC and noticed
that the assemblies had indeed been registered. The problem is that the
assemblies that are registered are for Preview 4 (I verified this by
opening them in Reflector and observed that the
System.Web.Routing.StopRoutingHandler class was non-existent) and I have
been unable to unregister them.

In an attempt to recover, I uninstalled Preview 5, which did not
automatically unregister the assemblies. I then proceeded to attempt to
manually unregister the assemblies. Running gacutil /uf resulted in the
following error:

Assembly could not be uninstalled because it is required by Windows
Installer

At this point, I'm not really sure how to recover from the error. In
all honesty, I'm not sure if the Preview 4 installer registered the
assemblies in GAC or if I did it. All I know is that I can't get them
back out!

Any ideas on what I can do to recover?

Thank you in advance,

Sean

By the way, I forgot to mention that my development machine is running
Windows Vista SP1.

Fao, Sean wrote:
I've figured it out. The assemblies had a pin in the registry. To
remove them, I went to
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Installer\Assemblies\Global and
removed the keys.

Hope this helps somebody else!

--
Sean