If you run windows, your likely using something that's vintage and you don't even realize it. Take the calculator, or even windows explorer, its just been updated and made to look nicer. Or, even some of the vintage games like.. Minesweeper
On the other hand, they do recompile the source with each iteration.
and saying windows explorer had "just been updated to look nicer" is kind of inaccurate- It's nearly doubled in size since windows 95, and that isn't just resources.
For the sake of clarity let's use the file date of the EXE to separate the old from the new. Especially since a lot of the applets got minor changes, not the least of which was the use of the XP look.
Anyway, back on topic-
I'd have to say QuickBasic or Visual Basic for DOS. Heck, even Windows 3.11 gets honourable mention.
(yes I do use it, I have it on my old laptop)