slow network..how to speed up

i have a 13 pc (mostly windows 7) network with dsl internet, one wireless printer, a netgear F726T unmanaged switch, and a server running windows server xp.


it has become super slow trying to access or save "stuff" to the attached server.

what can i do to greatly speed things up?

new switch?

new server?

new isp?

would switching the server to a NAS help at all?

thanks in advance