Wireless problems with Mac and PC

We have a MacBook and a desktop PC. The MacBook connects to the wireless network using AirPort and the desktop is using the D-Link Airplus G DWL-G122 Wireless USB Adapter that came with the router. When the MacBook is connected to the internet, the PC has very limited or no access to the internet. how do i fix this? does it have something to do with the IP adresses?