I installed linux for the first time in 1992 on my parents DOS machine. I had another partition for it. It was Slackware with kernel 1.2.13 I think. All off 5.25 inch floppy disks.
Setup wasn't so simple then and I was a UNIX Noob so I managed to set the swap partition to the DOS hard drive and overwrote the first 4MB or so.
The FAT filesystem's root directory and many others were blanked but not all files were lost. Norton tools and CHKDSK managed to get a lot of files back but many of the wordperfect documents were in the form "FILE0001.CHK" and no way to know what was in each one other than very laboriously opening all of them and trying to work it out from the contents.
Very fortunately I had an old backup but the problem was to know, out of all the recovered files, which were covered by the backup and which were new since the backup. If I could ignore the files that I could restore from the backup then I only had to load and rename the ones that were new.
CHKDSK couldn't recover the file size since that was in the destroyed directories. So you couldn't guess if some backed up file matched a restored one just by looking at size.
In the end I wrote some perl+shell to get the md5 of the first kilobyte or two of all the backup files and all the recovered files. I used this to match files and get a list of all the recovered files with no corresponding match in the backup. These had to be new files and since there were far less of these I could manually load up each one into Wordperfect, see what it was and give it a sensible name.
This program (don't have it anymore) saved my bacon and served no-one else but me. It took me from despair to triumph and that's why I like it so much.