Can i have WLAN & LAN both at same time?

Hi.
Im trying to connect a few pcs to my lan through a wireless connection.
I have an access point near those pcs, connected to an hub. I have one XP on my lan with a wireless nic which can communicate with those pcs. Its all fine.
But…
I cant have that XP on the LAN when its working through the WLAN and i cant have the wlan working when the lan-connected nic is enabled.
Im looking for a way to have both connections working at the same time.
Am i looking at this the wrong way or is there some config i must do aditionaly?
Thx!