About the PCs running the test software, I suppose that you are using some old version of Windows OS -- maybe Win98/XP. Am I right
Actually some of it goes back to DOS, Windows 95 as well as 98 and XP.
There are 3 OS aspects:
1. Development environment- will you be able tol go back and recreate it to modify the code. Something I really hope to avoid.
2. Operation under a newer OS. Microsoft is normally quite good with backward compatibilty with the glaring exception of point 3, below
3. I/O Drivers- which is far more problematic as Microsoft scaled back first on the parallel port and then the serial port. Some USB to serial port converters work well.
A bigger problem is the changes in hardware architecture and the maintenance thereof- there is the ISA, PCI etc architectures and there is an added complexity in that sometimes you need a system to configure the hardware in situ- so make sure that all you need (software as well) can achieve this on whatever hardware you have left if you ever need to repair/reconfigure.
Also the storage medium can be a problem especially (as Duane noted) if you have everyhthing on 5.25" disks, and you only have 3.5" dirves if you are lucky.
...The JTAG/SWD capability is more for development debugging than for production testing.
Which brings up the point that the test techniques and tools requried for production test are (or can be) significantly different from what is requred for development. After all by the time you get to production you presumabley have a working design and you mostly need to check that it's built right and has the right firmware and calabration values loaded if necessary.