Okay... I have a system setup with D-Link Wireless Router and two computers wired to that router. I have a laptop wireless connected to the router. The distance between the wireless router and the laptop is about 40 feet with a concrete wall separating them. Also, between the laptop and the router I have a D-Link Range Expander. I am not using WEP. I am using MAC filtering. The Dell laptop has a built-in wireless card and is the only hardware component that doesn't match the other D-Link hardware. I cannot get a consistent high quality wireless signal to the laptop. It is strong than weak. Sometimes the signal is so week it seems as if I am using dial-up on the Internet. Any suggestions?