Thanks for your response.
I have tried different security options, WPA has never worked for my computer, so with the advice of Belkin Tech Support, we tuned it down to WEP 64. Have not tried "No security".
I have not tried setting the router to B & G only, I am not sure how, and Tech Support did not suggest it.
The card does see the network but will not connect, or will connect for a couple of seconds, and then goes right back down. There are no error messages except - "Cannot connect to wireless network". I have tried using both the Windows network control and the card's network control.
I spoke to my service provider and had them take a look at the connection. They show the modem working fine, but no router attached! I keep having to unplug it for reset.
I have downloaded and installed all the recommended Dell updates for my LAN card.