If it has 4 gigs of ram and is a 64 bit machine, you’d be crazy to not load Win-7 64.
If it’s 1 gig of ram you’d be crazy to not load XP.
The system will be a 3Ghz AMD Athlon II CPU, Asus motherboard, 2GB DDRII ram (probably add more as soon as I get it), SATA-II hard drive and DVD Burner