I tried this on Microsoft Windows XP 32-bit, Microsoft Windows XP 64-bit, and Microsoft Windows 10 64-bit. It didn't work on any of them, but failed in slightly different ways on each. I purchased the original Rainbow Six CD from e-bay and that works fine on Microsoft Windows XP 32-bit. How do I get a refund for my GOG purchase?

The refund documentation should be on support on gog website.
Had extremely strange issues with the gog patch 2 of rainbow six. The retail cd exe and version should run under Windows XP SP2 compatability mode perhaps on Windows 7 or greater.

It is missing the multiplayer server that people could still use for LAN offline --RainbowSixMP.exe, unfortunately. It still has the Mplaynow exe... don't know much about it.