I am running a wireless network from my verizon router, but I have an Airport Express so I can play music wireless (but the airport express is NOT creating the wireless network). Everything works great on my Macs, but my sister recently got a PC and I am unable to get it to connect with the airport express. When I scan for the Airport Express, it doesn't appear. She has the latest version of iTunes but Airplay does not appear.

Anyone have any suggestions? Thanks.