dan, 1 year ago (edited 1 year ago)

Plenty of old apps still run fine. I’ve got VB6 apps I wrote in the mid 2000s that still run. A previous employer has DLLs from 1999 still running in production on Windows Server - VB6 COM components with hundreds of thousands of lines of code in total. I’m reasonably sure than Office 2000 still works, too.

You do sometimes have to change the compatibility settings and run the apps as administrator (since they were designed for Windows 9x which didn’t have separate admin permissions) but often they work.

Even some 16-bit apps work fine as long as you use a 32-bit version of Windows (Windows 10 or older; 11 dropped the 32-bit build). The 64-bit versions of Windows don’t have the NTVDM component that’s required to run 16-bit Windows and DOS apps. It’s an optional component on 32-bit Windows and you need to manually install it.

A lot of effort is put in to backwards compatibility in Windows - Raymond Chen has blogs and books about it.