wireless network between mac and pc??

what is a suitable wireless usb adapter to use for an imac?i want to set up a network in which the netopia wireless router is directly connected to the pc downstairs and the imac upstairs is connected with a wireless usb adapter. all the adapters which i have looked at only state that they are suitable for systems running windows. i have very little knowldege of macs but i assume if the adapter works via the usb port there must be some adapters which are compatible.any help much appreciated.