QUESTION FOR COMPUTER GURUS

OK, I know there's got to be somewhere out there who reads this blog who knows a thing or two about computers. Hopefully, one of you will read this and have an answer for me. So here's the deal:

My wife's laptop (a Compaq Presario running Windows XP) died last year. A few months back, a gal she works with offered to bring it home for her husband to look at. He's pretty good at fixing hardware issues and she figured maybe he could repair it. Long story short, he managed to revive it, and it works well now. All except for one thing: it won't connect to the internet using our wireless network.

The computer finds and connects to the network without a problem, but it can't seem to acquire a network address. I've tried plugging the computer directly into the modem, and it connects with no problem. When I unplug it, a little balloon over the icon in the systray says "a network cable is unplugged". All the while, the little icon next to it tells me it is "acquiring network address".

I've tried rebooting. I've tried updating the modem's driver. I've tried repairing the network connection, but it always gets stuck on "renewing your IP address". I've tried disconnecting and reconnecting to the network and retyping the network key to ensure it is correct (it's a secured network). I keep getting the same result.

So if anybody out there has any ideas, I'd be glad to hear them. Your help would be greatly appreciated.