What do you mean with
My former ID files have suddenly turned to PS files?
- They have turned to Photoshop files?
- They have turned to PostScript files? (You should not use postscript at all in modern days.)
- They have changed their file association to Photoshop?
You should make a virus check anyway on a regular basis. It will detect if you have one.
If it is a problem with the file association you should change it on your OS level.
If InDesign is making problems you should delete saved data and the preferences. If this does not help you should uninstall it and install it from the scratch, never use any migration from a backup or any other computer.
Sounds like ID did not shut down properly and the recovery data is corrupt. Enable Windows Explorer to show hidden and system files, then go to C:\Users\<Your user name>\AppData\Local\Adobe\InDesign\<Version Number>\<language>\Caches\ and empty the InDesign Recovery folder. That should allow ID to restart.
If the file associations are damaged, it indicates a problem with the icon handler .dll file and the best fix is to reinstall the program. You can reset the Association in windows, but that will show only the latest version icons, rather that the correct version icons for older files.