I used 7-zip to open a file on a different host, using file commander as my network browser. When I tried to open the remote zip, I received a permissions error. At that point, EVERY runnable file became associated with 7-zip. Exactly what this user reported, http://answers.microsoft.com/en-us/windows/forum/windows_vista-windows_programs/7-zip-associated-with-all-programs/972d4793-4521-4a01-ab5d-6637e7148622. In my case, I was lucky that I could access the windows help program without running an exe. From there, I was able to open a browser window and from there, able to go to here, http://www.winhelponline.com/blog/file-asso-fixes-for-windows-7/, and download registry fixes. I certainly did not want to do this, as the server I downloaded the fix from was untrusted, but I had no choice.
I immediately uninstalled all instances of 7-zip from all my computers.