Long file names (Score 1)

The worst thing I ever did was back when I was just getting introduced to Win 95 (sadly, prior to my linux days). In my never ending effort to milk more performance out of Win 95, I got the idea to boot the computer into old DOS 6.2 and run Norton Speeddisk on the Win 95 disk, so it could defrag the files Windows defrag could not. It did. And replaced every single long file name on the disk with it's 8 character dos compatibility equivalent. As it was my only machine at the time, and reformatting wasn't desireable, I renamed every file by hand... :(