I don't know much of anything about the Sark100/MNI60 analyzer, but I did do some quick research on it and this is what I came up with.
The windows software for it requires Windows 7 or newer. That seems to be due to the .NET Framework version that it uses. It also requires Microsoft Excel to be installed to save the data in spreadsheet format because it uses the Excel library to generate them.
I've been a programmer (non-professional) for over 20 years and using a proprietary library (such as in Excel) that isn't free/easy to obtain is just idiotic. The software will work without it, from what I've read, but it'll get errors about saving things after running a scan. I don't have one, so cannot confirm. The software not working on Windows XP isn't a surprise though. That OS was released in 2002 and has long been unsupported. The software compatibility between XP and Windows 7 or 10 is often poor and can be troublesome to do when designing software and it would be easier to just program 2 separate versions of the software. Since XP is a mostly dead OS though, most developers don't bother when they write a program.
I did find a GitHub repository for a custom version of the software that runs on Linux or MacOS. That is here:
https://github.com/coddingtonbear/sark-100-antenna-analyzer
Again, since I don't own the analyzer, I can't confirm the usefulness of the software.
As for the FTDI USB-to-Serial interface chip inside the analyzer, they can be troublesome. The legit chips work great and are trouble free, but there are so many different Chinese clones of that chip, that it is somewhat difficult to find a real one. I would imagine the analyzer uses a cloned chip. The clones can vary in how well they work and how well they cooperate with the FTDI drivers. The only place to get the official drivers is from here:
https://www.ftdichip.com/Drivers/VCP.htm
They have the drivers for every system that chip can officially interface with on the USB side. The chip just shows up as a COMn serial port when it's working and the analyzer software handles everything else.
I do hope you get your antenna analyzing troubles sorted out. Not sure if any of this information will be helpful in any way, but good luck and 73.
- Brad