Choosing the wrong program to run a file

I attempted to choose a program to run a Windows prefetch (.pf) file and chose the wrong one. Nothing happened.

I did not realise that the check box saying 'always use this program to run files of this type' was ticked and now all the .pf files in the folder are now associated with the chosen program.

Can I undo this mistake? and how would I go about putting back everything the way it was before I messed up?

 

You can run a System Restore using Windows Help or select another application to use by opening My Computer, right click any file with a .pf, selecting Open With, Choose Program, and checking the box: Always use...