running xp on all pc's - have one with lan connection to wireless dsl modem -works fine - gets on line ok -other pc with wireless usb adaptor - correct ssid -100% signal strength -sees the ssid -has the network key - seems all ok but cannot connect to internet -have cleaned everything -have used zero configuration but still no connection - any ideas to solve the problem

Sounds like it could be a security setting.
Firewall or internet browser security setting.
Check Windows firewall setting, disable it then check to see if you can access the internet on your wireless connected computer. Also disable any other firewall, such as Symantec internet security or McAfee, while testing your connection.

If no sucess check your security settings in the browser.