Now also tested on Vista x64 (in close cooperation with worstje), and we concluded that both the x86 and x64 VC++ 2010 redistributable packages need to be installed on a x64 OS to get this thing up and running. The new installer just takes care of that, and also installs the .NET 4.0 Client Profile, if no .NET 4.0 runtime is found. It's downloaded fresh from the MS servers during installation, and automatically includes the proper language pack for your OS, for as far as we could see.
Now worstje is ironing out the last wrinkles, so we won't have to wait much longer for the official release :Thmbsup:

Just re-registered the DLL after installing VC++2010 using my test-installer, and it ran just fine. I now have a contextmenu item in Explorer. Would you want to use languages besides English in the installer? (the script I started with has German beside English, and it can be removed or expanded to some extra languages (nl?), but it would take some extra work, but I don't mind, just tell me your preference(s))
In the meantime also tested the 'Enable/Disable context menu option from settings', and that works just fine, both to Enable and Disable.

If you can provide me with your Inno script I'll add the snippets to enable the Download and Install.

Further testing in Server 2003 x86 and Server 2008R2 (x64) after this post and a cup of coffee :D