Difficult to Answer
As Windows 8 is not out, depends what you mean by "productively" as DesqView and DOS 5 are so ancient I have serious problem knowing what you could with such OSs. You would certainly have a problem using the internet unless you just like text. I don't think there is a web browser You would only be able to connect to the internet via SLIP or PPP.
I doubt you could record sound.
Printing colour would be very difficult. Inserting pictures into text documents? Possible but not easy. .Creating web pages would be tricky. No web browser.
You wouldn't be able to make a powerpoint presentation.
Modern PCs and OSs make people far more productive certainly in work. Ask any Secretary or PA.
Your whole set up sounds eccentric. If you have been using it for donkeys years and it satisfies your requirements then good for you. You cannot enjoy the pleasures of 21st century web browsing, video, music and other what you call non-productive tasks, but then maybe you don't want to,
Windows7 is a lot more useful than DOS and a lot more fun!!