Problem
If you go in Explorer to the GAC folder (%windir%\Assembly) a shell extension gives you a special view of the content there:

In this view you couldn’t copy the DLLs to somewhere else.
Solution
- With a special registry intervention you could deactivate the shell extension so that Explorer shows the content in a normal way.
But this is like a hack.
- If you are practiced with command line you could go to the assembly folder
- And the smartest with explorer is to map a network drive to \\<your machine>\c$\windows\assembly
and so you have access to your assemblies over the new drive: