How to change Open with Settings for a EXE File.

I am network administrator of a 50 PCs computer Network. One Operator in my network Selected open with vlc player for Exe Files now all my Exe files opens with vlc player. I have very important Data on my PC and I want to short out this Problem without reinstalling my PC. My Window Stop workings please provide me Solution for this Problem and tell me how I can set default Open with Settings for a EXE File. Regedit is not opening at this time.
