having been through this nightmare, myself, I would advocate the following.
I'd get a hard drive of the same size - and ghost the master to slave (there are lots of products on the market that replicate drives at the bit level).
Once copied, replace the existing drive with the duplicate drive and then install windows 10 (professional or enterprise) on the duplicated drive and let it run it's course.
It may not find the drivers it needs but many times it'll use the older windows 7 drivers to communicate with you hardware.
If it works, you've got a backup in time of the original drive.
If it fails, well, you've got a spare drive to backup to locally within the machine after you figure out how to upgrade it.
9 out of 10 times, it works fairly well - but you really won't know until you try it.
If all else fails, you put the old drive back in the box and you've lost some time while you figure it all out - but you've not lost your original configuration or drive.
The other alternative you have is to remove all connectivity apps on the windows 7 machine (e.g. Internet explorer, firefox, chrome), modify the firewall to shut down all network ports (TCP/UDP) except what your software requires to communicate with and put the box in a corner so it's not used except for recording. If it's never on the internet, and it's not used as a desktop for anything else, that should "sandbox" the device safely until you find a way to upgrade or change it.
Josh