RegEdit Warning: This post contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, Microsoft Knowledge Base article 256986.
OK, with that out of the way... you have to remove the install reference for the MicroFour License DLL before it will let you delete it:
Browse to
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion\References\MicroFour License, Version=1.0.0.0, Culture=neutral, PublicKeyToken=4a99020e74365197, processorArchitecture=MSIL
with RegEdit.exe. Once you're there, delete the GUID key that's below that key. Should be either {2EC93463-B0C3-45E1-8364-327E96AEA856} or {B02F9D65-FB77-4F7A-AFA5-B391309F11C9}. Once it's deleted, you can go to the C:\Windows\Assembly folder and delete the DLL and re-run the activation client.
We added that stupid install reference in some of the versions of the Activation Client, but we've since removed it since you end up with the same problem you're having now... .NET thinks something is dependent upon it and it won't let you remove it.