How do i set up a network for 100 users??

I’m trying to build a network for 100 users that needs to be reliable, have an impeccable disaster recovery system and have other security features (ie. firewall, anti-virus software, and anti-spam.I have to use Windows Server 2003, Exchange & ISA.

I guess my question also is.. are there any resources that will show me how to create this complete network??? And also what would be the best router switches, security appliances and backup systems to use on the market today. I have seen some that are good but not great. I jus wonder where you guys get your nodes from. Thanks!