i would suggest to delete C:\ProgramData\FAForever folder
NOT PROGRAM FILES
Programdata is a hidden folder. Don't delete whole programdata, only Faforever folder inside of it.
it also contains replays AFAIK, so if you want to keep them then don't delete them.
Basically this whole folder and things inside of it will be created automatically when you run FAF and use it.
FAF will redownload patches and re-create C:\ProgramData\FAForever\bin\ForgedAlliance.exe
and if you run FAF without admin rights (as you should) then it should create things with correct permissions and it should keep working
(If you ran FAF before with admin rights, it could have created files that only admins are allowed to run, and afaik that could be not the only problem, so just delete folder, and don't run FAF as administrator)