mattjax05:
nads:you need a wireless router.
Sorry to come across as dumb but is there a reason why you need a router?
I understand the Airport Express can stream music wirelessly from a PC without a router via Airtunes.
Your music is stored on your computer. Somehow it has to get to your Duet receiver.
It does this wirelessly by using your existing wifi network / router setup to send the signal to the Duet.
The Duet "sees" your music collection via your wireless network.
Squeezecentre itself does not stream the music - it just organises your music collection so the Duet functionality will work.
You could plug your Duet receiver into your PC / laptop by ethernet cable but (obviously) this would not be wireless.