At a loss now. the only other thing is that maybe it is locked as virus scanner thingy or locked by another app or the aircraft is locked in a protected folder ?
Try: to rename the aircraft.cfg to aircraft.txt , then delete the original aircraft.cfg.
Then rename aircraft.txt to aircraft.cfg.
If that doesn't work, (cause the file is locked or unable to be copied for some reason), open aircraft.cfg with notepad> Copy all of the text in the file.
On your desktop, right click New> Text document name it aircraft.txt. Open the file with notepad, paste all of the txt into the file. Save, Close.
Delete the old aircraft.cfg, On your desktop, rename aircraft.txt to aircraft.cfg and paste that file to it's original folder location.
Or something like that!!