Help needed with connectivity

I am using a laptop on a wireless network served by my hardwired P.C. which recieves Sky Broadband. Recently I keep losing connectivity even though when I connected the signal strength may have been excellent.
Sometimes reconnection is straightfoward and quick but at other times it gets stuck on aquiring network address. Sometimes it won't reconnect and it is usualy because no network address was assigned to the computer.
I have checked virus problems and cleaned the registry and disk but nothing has helped.
Any ideas please but please beare in mind that I am a novice so simplicity would be appreciated.