Sometimes you gotta do the unthinkable. In 2000, my employer (a university) migrated the accounting/student records/class records system from an ancient custom in-house bunch of COBOL to a shiny new commercial system that used MS-SQL as the back-end. All good and fine. Except the one elderly lady who was the Accounts Receivable manager. She still went into the old system several times a year to check to make sure potential grads and students requesting transcripts didn't still have charges showing in the old system. So this meant we couldn't nuke the old system off the file server - it was maybe 350 megs, which was quite a lot back in the days when RAID arrays were still found built out of 4-Gigabyte SCSI disks. So we had to leave the system in-place.
Fast forward 13 years, and she's STILL using that old system, even though no new data had been put in since late 1999. Still double and triple checking that students didn't still owe the library 50 cents in late fees from 1995. We asked her to stop, begged her to stop, but she'd started using that system the day she stepped off the Mayflower, and damn it, she was going to continue. We even got her VP to tell her that she needn't run that check any more, to which she responded "It won't hurt anything to just check."
Finally, late one night, I'd had enough. I went in and opened a few of the many, many data files and started randomly flipping bytes. Not a lot of files, and not a lot of bytes, mind you, just enough to cause problems.
For months, I didn't hear anything from her about it. Then, a few months before she was due to retire, I got The Call that she couldn't get into the old system. Hadn't tried to go in for six months, and now she was getting weird errors. "Ah, it appears the data files are corrupted, let me restore from last month's backup... Nope, it's bad, too. Sorry. Enjoy your retirement."
Deep down, there's a little Bastard in all of us.