Servers:
1 dual homed server for services (e-mail, web hosting, NAT/Firewall, controlling station access, etc. - 1 or 2 medium speed CPU (600-1000MHz), 512MB+ RAM, FAST RAID disk (4 disk 0+1 IDE should be fine) Windows 2K or Linux.
1 internal secured database server for customer info, accounts, etc. database. This can also be used as the office workstation.
Workstations:
If you are going to provide gaming (Quake3, etc.) you'll want high speed CPU's (Athlon XP 1700+, P4 1800, or better) & graphics (ATI Radeon 7500-8500, Nvidia GF3 or GF4 Ti) & memory (256MB+ DDR266 or PC800 RDRAM). If not, 1GHz or better Duron or Celeron with decent graphics and 128MB RAM will do fine. I recommend Windows XP for the desktops for remote control capability - help users without getting up, etc. Win2K will do if XP won't.
Definitely use 100Mb SWITCHED ethernet for the local net.
¿qué país?
I thought a thought, but the thought I thought wasn't the thought I thought I had thought.