Coming back to hobby

I started out with 2000 and went on to 2002. I ran dual screens, looking back 2 enormous 21" CRT's. I purchased 2004 but with changes in family circumstances Flight Sims were put on hold. I am now semi retired and have the time and enthusiasm to take up the hobby once more. If I am to base my system around 2004, probably running 2 screens with windows 7 what pc specifications should I be looking at. I dont know if 2004 runs on windows 10, but not a fan of 10. So basically I would like to use a dedicated pc for 2004 and would appreciate any comments on ram, processor and graphics capability.