Hello Henri,
http://scn.sap.com/people/s.sriram has posted a quite useful document which shows how the SAP GUI 7.40 can be downloaded: http://scn.sap.com/community/gui/blog/2014/12/03/download-and-install-sap-gui-740-with-nwbc-50
Just one thing to add: the first steps to find the download page are:
- Home | SAP Support Portal
- Click on "Software Downloads" in the upper right corner
- Click on "Installations and Upgrades"
- Click on "Alphabetical List of my Products"
- The rest can be found in the document.
Best regards,
Laszlo