Installation on Windows 8.1

Question

I am trying to install PT 7.5 on a new Windows 8.1 computer. After installation, I supplied Paratext name and code, but the OK button remained gray and could not be pushed. Then I uninstalled 7.5 and tried 7.6beta. This one failed and asked me to open PT7.5 and untick the choice of alternative rendering. That was impossible, since I could not get 7.5 started. Uninstalling 7.5 did not help, since the same message appeared.
I have not seen this before. Any help?

Answer 1

After downloading the online installation of 7.5 it worked. I suspect that it could be a virus problem in the computer, as it came with trojans from the shop.