How can I match the the wireless protocols on my computers?

When I listen to music through my AirPort Express, it's great if I'm playing the few iTunes playlists on my iMac or my wife's PowerBook. But If I play my master playlists which are all on my Dell Inspiron 530, I get approx. 1-second silences every minute or so. Under "Speed" the Apple computers both say Standard 1500 MTU, so I guess that's what the AirPort likes. The Dell must be set to something else. How can I find out and modify it?