No offense to everyone else here, but I think you guys have got the wrong idea. All he has done is changed a program default, which isn't really a big deal. Okay, heres how to fix it. Before you did this, there was no program default and you cant revert back to that state, but if you right click the dll, then go to open with and then choose default program, you can change it to something else. I would suggest you change the default program to something like notepad, as that cant do any harm. once you've done this, your dll will appear as a notpad icon rather than a winrar icon and it wont try to open winrar any more. Any questions, just ask.