This is an old one, but it's served me well over the years. Have you ever wished you could dive into the GAC and see what was in there, maybe drop in some rebuilt assemblies or even debug with those assemblies?
There's actually as simple way to do this. All you're really doing is mapping a drive to the super-secret bunker that is the assembly cache. From a command line, use the subst command:
subst [drive letter]: %windir%\assembly
I use drive letter G: (for GAC, duh!). Once you run this command you can Run > g: and a file explorer window will open on the wonderful world of the GAC. You get all its greatest hits: GAC; GAC_32; GAC_64; and of course, GAC_MSIL.
I would highly recommend backing up the files that are already there, however.