Hi there , I was using cubase AI5 which was installed on my PC but I wanted to try Cubase 7.5 trial version 
so for that I un-installed the cubase AI5 and tried to install Cubase 7.5 but it wouldn’t open on my PC so I un -installed it via perfect un-installer software and now I am trying to re-install cubase AI5 it gives an error so what can I do now? I have sent a screen pic to show this :
Don’t really understand, but, what I would do is the following uninstall everything, Restart, then install what you need. This first, if it does not work do the same again but before restart search for all Steinberg folders and delete them manually, you could loose settings of course.
Hello,
It seems that the uninstaller deleted crucial components of the eLicenser Control Center as well.
We do not recommend those tools you should only use the un-instal feature from your control panel.
Please download and install the latest version of the eLicenser Control Center from the following link:
Best regards,
GN