Serene,
Sounds like we do it much like Wayne. We are happy with a simple peer-to-peer network with one Vostro acting as the "server". The network is all Vostro's. It is not that we set out to do it that way, but we started with a couple and have been happy with them, so as we upgraded, that is what we used. Each time I would go to Dell and think "maybe I should upgrade a little and get an Optiplex", I would compare specs and reach the same conclusion as you. The Vostro's are basically the same machine in a different box with a higher price tag.
So we have 5 Vostro's,
The "server" a 2205
intel core 2 duo 2.93 ghz
300 GB hard drive
running Win 7 Pro
One 230, exactly the same as Wayne's above, also Win 7 Pro.
Two 200's both with core 32 duo's 2.40ghz
Both upgraded to 3.24 of RAM
running Win XP
One older Vostro (would have to look up the info)
Pentium 4 @ 3 ghz
2MB RAM
Win XP this one runs a bit slower but gets less use.
