The point is you have equipment that is worth millions of dollars and even more in downtime that is reliant on half baked software made by the OEM to only work on there equipment and will only run on say 95.
Its not a mater of won't upgrade, its can't upgrade. Had this not so long ago, one farsical example up until a couple of years ago still required DOS. Hell being able to use XP on these things would be a god send.
I understand the problem, dont worry! When it comes to commercial gear, its absolutely piss poor that manufacturers dont provide an upgrade path. I see it all the time, and old PLC used in a factory that is 30 years old and the only software is dos based. Factory is running around the clock, so why bother upgrading all the controllers? Down time = lost money, upgrade time = down time. Its hard to justify.
I had one case just recently, software written for DOS. I tried to make it work under XP, gave up and rewrote the software for Win 8. Took me all of 3 days. Lucky for me it was an inhouse product, so I had access to the source code.
Just thought of another example where upgrade to win 7 is a problem.
We have a piece of software that we designed for reporting and tracking of hardware faults on a casino floor using mobile terminals. The casino is doing the Win 7 upgrade thing at the moment, and when they ran out client side software, they discovered they cannot print. So I load it up on win 7, sure enough when you hit the print button, it no longer shows the print dialog box. So reading around, this is because MS has upgraded the print dialog box in the API to use the new Win 7 look and feel. To make it work is simple, you just have to tell windows to use the old interface. Easy fix, and we roll out a new version of software. Imagine this was a large software package used for commercial environment like a bank, not so easy to fix.