Hey I have a PC running 98SE ;-)
I feel for those who have to support an OS no longer supported by the vendor. That's a tough position to be in, not only if a customer comes across a bug that is due to the OS, but it keeps you from advancing your desktop application forward.
You can always have legacy builds for older systems and use shiny new features inside conditional compilation blocks. Or check at runtime and let newer operating systems use the new features. Yes it takes care and a little more testing to keep supporting older operating systems but your users will love you for it.
I’m always kind of sad when a developer says to a customer “your OS is too old. We are dropping you on the floor.”