itch.io

you cannot run modern Unity engine on 32bit OS. i dont think the devs can change that on current engine. Im sure you have reasons but upgrading is long past due. windows so old is an open door for bad actors. 

Going along with Saltine404's comment, due to the fact you need to be at least windows 10, I belive. The devs could change the ops system, but it would also leave vunerabilities for bad code and malware to enter undetected and for your (and their) processes, servers, and so on to be attacked easily.