DOS all the way!
I actually still have an application running at work I wrote back in 1990 using Paradox 3.0 for DOS. They use it daily to reconcile and it still runs under XP. For some reason, they want me to rewrite it!
I can't comment much on the Windows management stuff because I've only done a little network management when our company was downsized. I learned a little Novell when I was 1 of 4 people in our MIS department and somebody had to set up new users. I started to learn the Windows NT stuff but fortunately they decided to hire more people.