Back in the day (late 90s), the entire business of Bankers Trust (bought by Deutsche Bank) was on a ginormous spreadsheet macro written for the 16 bit Lotus 1-2-3 under Windows 3.11.

The thing was around 20,000 lines of code (Lotus-script if memory serves). Written by a business analyst. No indentations, no following good coding practices, no comments, tons of variables called a, b, aa, bb, etc...

All attempts to make it run on Windows 95 and later on Windows NT/2000 failed. It was unclear why. Something would always be wrong. At some point, IT managed to make it run in a VM on an early VMWare version under Windows 2000.

Sometimes you gotta do what you gotta do.