(Only half-joking here. I know it sounds like it's an important client, but it seems as if there was a serious breakdown in communications on the client's part, _and_ they're stuck on obsolete technology. These are not realistic requirements.)
I suppose option 6 would be to figure out how to get the client to upgrade their systems to a modern hardware and OS, and then run the old software in a VM instead.
1. Requires a dongle attached to a parallel port for it to function. 2. The company who made it went out of business over 15 years ago.
They have plans in the future to migrate to linux, but that isn't in the card for a few years unfortunately.
1. You probably don't need it. I don't know about the legalities involved here or what the specific license is, but there's probably a trivial way to circumvent the hardware requirement, especially with a VM. Back when Windows 2000 was a thing, people were still using MD5, and nobody was using secure elements. Worst case scenario, they've got some of the actual program logic on there, and you'll have to either reverse it or replace it. Again, not commenting on the legalities here, but seeing how the software was (presumably) legally licensed and the company is long gone, it couldn't hurt to ask the lawyers whether they think it's safe.
2. You can pass a parallel port through to a VM if you really must.