As per http://msdn.microsoft.com/en-us/library/9x295t9k.aspx
"In earlier versions of the .NET Framework, the Shfusion.dll Windows shell extension enabled you to view the global assembly cache in File Explorer. Beginning with the .NET Framework 4, Shfusion.dll is obsolete. "
Consequently, something that has worked since version 1.0 of the .NET framework is now [cough] "broken" - no more going to C:\WINDOWS\ASSEMBLY anymore! Now you will just get the ugly view of the GAC internals.
There are 3rd party utilities to help you browse the GAC (e.g. .NET Reflector can help in this regard) - but it is simple enough to just pipe or redirect the output of gacutil.exe to a text file to read in your favorite text editor:
C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC>gacutil -l > c:\temp\gacu