GEWIS is part of the MSDN Academic Alliance (MSDN AA). With help of MSDN AA students are able to obtain Microsoft software for free. Microsoft’s operation systems, servers and developer tools are available through MSDN AA. Obviously there are also serial keys for those programs.
For more information you can go to the official MSDN Academic
To use MSDN AA you need an account for the GEWIS-website.
You can create one using this link, if you haven't done so yet.
As soon as you have an account you can log in using the below link.
You can log in using the GEWIS members-page.