Here's the setup:
1x MacBook Pro (Snow Leopard) connected to the internet via Airport Express
1x MacBook Air (Snow Leopard) connected to the internet via Airport Express
1x Airport Express connected to the DSL modem via Ethernet
1x PC (Windows XP - Chinese OS) connected to DSL modem via Ethernet (no WiFi)

Here's what we'd like to do:
Connect all 3 computers on a home network (mainly to combine, store and share video and audio collections on the PC - freeing up much needed space on the Macs).

Question:
Is it possible to set up a network where the only common denominator is the DSL modem/router? If so, how? (pictures please, as I can't read Chinese to set up XP)