It is not an unusual situation at all. I worked for a tech company that as of two years ago still did not have any computers beyond XP and had a number of tools still on NT and even some on DOS/Win 3.1 and we had a huge IT staff. The problem is that we had a lot of proprietary software that was mission critical that was very expensive to upgrade to work with new operating systems and tools that couldn’t be upgraded for a reasonable cost or was impossible because the vendors were no longer around.
I've run across the same a time or two. I guess that the solution would be to start reviewing applications to make new purchases less proprietary and less likely to choke on newer platforms. I'm running an old WinAmp that was around with Win95 on a Win7 platform. I realize it's a lot less complicated than some of the huge apps that businesses need, but I find it difficult to understand why folks keep painting themselves into corners by having special apps contracted for development with no plan to upgrade after a certain expected life span. The companies that develop the software are the biggest winners.
On the flip side, we also try to adapt COTS apps for other than the originally intended use and that creates its own ball of wax.
I believe that quite a bit of medical software will run only on XP.
There's a machine tool in my plant that is controlled by a 286 running Dos Shell.
Coming upon that was like discovering a living brontosaurus.