In general it is strongly recommended to use a compatible wifi router. In that way several devices can be connected at the same time and the connection is less prone to interference.
Proceed as follows to set up the PPTP VPN connection under Windows 7:
Go to Start → Control Panel
Select Network and Internet
Open View Network Status and Tasks
Click on Setup a new connection or network
Select Connect to a workplace, then next
Select Use my Internet connection (VPN)
Enter vpn.stw-bonn.de as Internet address and e.g. StudNet as Destination name, then next
Enter User name and Password
The user name can be found in the registration e-mail, which you received after sign up on https://startup.stw-bonn.de. The password is the one you chose at registration.
The connection is set up. Please click Close
Left-click the Network icon in the System Tray
In the new opened window select the new created VPN connection (here StudNet ) and click Connect
In the new connection window click on Connect to start the VPN connection