While I'm not familiar with that game specifically, it sounds like your hitting some sort of DRM issue where the retail game is stuck running in demo mode. My first bit of advice would be to check gamecopyworld to see if there's a crack and install it if there is. There may also be a cracked version on archive.org.
If that doesn't work, then it's likely the game is using some deprecated Windows feature, or doing something in a hacky or unintended way that's been patched out in newer releases. In that case, running in compatibility mode might fix it, but the chances are slim. A VM, like @wolfshadowheart suggested, would have a much higher chance of success.

If all of the above fails, the last hail Mary you can try before tracking down an era appropriate computer, is running the game in Linux under WINE. Ironically, Linux has better compatibility with a lot of old PC games then Windows these days, but it takes a bit of fiddling to get working.

Edit: Another resource to check is the PC Gaming Wiki. They have dedicated pages for most PC games, with a list of common issues and detailed instructions for fixing them.

I don't have many suggestions but for a lot of older games various compatibility changes may help. Things like changing the CPU clock speeds or possibly running it inside a VM can sometimes help.

Good luck, hopefully someone else has better suggestions than I!