Repair damaged ZIP files for free

This one just works, with a Google-ishly simple interface. To install click diskinternals.com zip-repair
Procedure to recover your zip file: 

1. If you can, copy your damaged zip file to the desktop
   otherwise, take a chance on unzipping in place on the floppy, just place the repaired copy on you desktop.
2. Launch the software  
3. Look in RECOVERED_... for the repaired copy of your zip folder.