I had just started using Promash a year or two before it ended. It was a rather difficult program to use and I had stacks of printed instructions to do various things that I had found online at the time. Like the OP I ended up with Beersmith (another steep learning curve) and have stuck with that. If I remember correctly the developers wife was diagnosed with cancer and he shelved the software to focus on his family.
I still use some of the functions it and I compare recipes written in other apps to see what they look like in PM. It’s still capable, viable,software.
if it was running on XP, you could get a virtual OS like https://www.virtualbox.org/ and install win xp on a virtual partition if not use some simpler and newer virtual OS. im on linux and there are a multitude of programs to run windows programs under different windows versions.
the virtualbox thing sounds like a pain but if you are fairly competent with computers you could promash going after an XP install in 20 mins or so.
Going by memory with the following. I may be incorrectly remembering as it’s been a while since I used ProMash. I don’t believe ProMash is so equipment dependent as BS.
I will admit, when I was using ProMash, early 1990’s, I really didn’t know what I was doing. I look at my brewing notes from that time and now think “What was I thinking!”.
I copied the 3 ProMash 3.5 floppies onto a USB drive and still the ProMash patch/update in case I ever need it.
I use it on Windows 11. It has a couple of minor glitches but nothing big. I basically brew one or two styles of beer and use it to keep a log of how the brews are going. I do the same with my online blog so when my computer crashes like in the past, I have brew sessions to go by.