i am going to say what u need to do when u going to use the STEN GUN 1) download it 
2) STOP do not replace the files. first go make a copy of the files u need to delete. and put it in a other map to save it for later
3) when done copy it. then replace the files with the new files
4) read the read-me file
5) when done read-me file and done what it says u go play it
and thats it 
how to get the old gun back ?
6) delete the new file(files)
7) put in the old files back and u are done
and thats about it. i hope this will help u how to get u old files of u gun back
ps. i didnt do it. but maybe it will work :s
