The final update for Windows 7 before it officially ended support on Jan 14, 2020 had (at least) one "minor" bug.

It was related to the wallpaper stretch function and could cause a black screen. Three days ago M$ released a bugfix update, KB4539601.

If you install that, neither tixati or fopnu will run.

Tixati version 2.67 is now available.

https://www.tixati.com/download/

A new Fopnu version should be released tomorrow.

This has been fixed with the release of Fopnu v1.43.

If anyone is still having this problem please start a new thread.