From
http://support.microsoft.com/default.aspx?scid=kb;en-us;306149:
"...you can add a registry key, such as the following, which points to the location of the assembly
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\.NETFramework\AssemblyFolders\MyAssemblies]@="C:\\MyAssemblies"
where
MyAssemblies is the name of the folder in which the assemblies reside.
NOTE: You can create the this registry entry under the
HKEY_LOCAL_MACHINE hive. This will change the setting for all of the users on the system. If you create this registry entry under
HKEY_CURRENT_USER, this entry will affect the setting for only the current user.
Restart Visual Studio .NET after you have added the key."
Translated:
Create a new key (eg "My Company assemblies") under HKLM\SOFTWARE\Microsoft\.NETFramework\AssemblyFolders\, and set its "(default)" value to the path of a folder where you'll put all the assemblies you want to make visible to Visual Studio.