I went to delete the original files, but I only got as far as "del *.COB" befiore hitting return.
I managed a similar thing but more deliberately; belatedly finding "DEL FOOBAR.???" included files with no extensions when it didn't on a previous version (Win3.1?).
That wasn't the disaster it could have been but I've had my share of all-nighters making it look like I hadn't accidentally scrubbed a system clean.