I still use a lot of features of MS-DOS in my programs, and all support Windows Xp (all service packs), vista/vista sp1, Windows 7, as well as 32/64 bits for every of them. Of course there are differences in the way each OS interpret some commands so I need to install the latest version of these on the different systems. I cannot do half of what my programs are doing without MS-DOS. Even though it's not capable of doing too sophisticated things, I do use the most powerful functions to accomply a lot of tasks. Next I have to acquire SSL commands to add to these DOS programs since DOS
I remember using DOS since Windows 3.1. It brings a lot of souvenirs back into memory ^^ Just prior Windows 3.1, I did not have any way to stock data other than the ridiculous amount of ram available. Playing Sim City 2000 would have been an overkill but also better game than those I had on my Commodore 64/128 (owned both)!! Oh well time has changed quite a bit.