Boot Camp Assistant 3.0 for Windows XP

I need to install Windows XP on my Mac mini (early 2009 compatible with Windows XP DVD) since that is the only OS that will run a specific software program that I need. I have the Snow Leopard disc but cannot figure out how to access Boot Camp Assistant 3.0 (apparently the only one that works with Windows XP) on it. I am currently running El Capitan 10.11.6 and when I plug the disc in, I am advised that the installer no longer works. When I search "optional downloads" I can find no sign of Boot Camp 3.0. I would be grateful for any helpful advice as to where to find Boot Camp Assistant 3.0. Thank you.