I have a problem installing to the Global Assembly Cache (GAC).

I have created a .NET dll

I can then install this dll into the GAC using any of the following methods:
-Copying into <Windows>\Framework directory using windows explorer
-Using Gacutil.exe /i Mydll.dll
-Using the GAC plugin for MMC

However after doing any of these. If I run Visual Studio, right click on the toolbox and select 'Choose Items...' My assembly doesn't appear in this list.
If I then browse to a copy of it - I can add it, but can someone tell me why it doesn't appear in the list in the first place?

Thanks