Python25/26 was installed in: C:\Program...\Python2...\ This is not the recommended path. Python25/26 always belongs to: C:\Python2...\
Recommendation: Install Visum and Python completely new: 1) Uninstall all Visum installations. 2) Uninstall all Python components. 3) Remove manually any folders like: - C:\Python - C:\Program..\Python - C:\Program...\PTV_Vision\... 4) Reboot the computer. 5) Download the current setup for the latest Visum release. 6) First, install only this current setup, including 'Python' (do not change its standard folder).