I'll test it today, does anyone know if that happen on win7 too?
Windows 8.1 x64
If I check the option to open the config.exe after the installation (clean install):
Are you running the install as admin? Are you able to run the config.exe file after that as admin or your normal user?
No. I tested on Windows 7 32bit and 64bit.
Can you tell me how your windows 8.1 computer is set up. I cannot reproduce your error.
How do you run the installer? Admin or user?
Do you have to enter the password for admin acount to install?
Do you have UAC activated and on what level? Did you change something related to UAC?
If you need help in answering these questions don't hesitate to ask