Lost Wireless-Help Please

Hi Everyone,
Sorry for such a long question.

Running XP on desktop with modem wired and connected to Netgear Router. Vista is on Laptop, for wireless connection. Worked fine since initial setup in July. Slowly lost connectivity over the weekend. Thought it was new neighbors interference. By Monday, no connection to network although meter shows strong signal. The LT & DT are not connected together for any sharing. Just sharing the router to be wireless on LT. Connected LT with cable today but could only get online through Netgear, not my named network. Don't understand that one. DL'd new wireless adapter drivers. Powered down all a couple of times. Read dozens of pages online but there are so many options. On the phone with Comcast, Acer, & Netgear. None could or would help but Netgear said it was safe to change the password in Network connections. That didn't work! Now the password box pops up when I try to connect and I have no clue. I don't think the password was the problem at first. Ipconfig was showing media disconnected. The router security password is still the same (I wrote it down back then) but the LT network password has a different amount of digits. I don't know what it is. Thought it was a code that Netgear had given me but they said no. When I type the router passphrase into network connections, it says that it's invalid. Are the two supposed to be different?

Can I just change the WPA passphrase in my router settings and use the same in the Laptop? Or, can I change my SSID in router settings and just add a new network with a new password on the LT? I'm kind of afraid to change any router settings since it was a difficult set up and done over the phone. More problems with ping and ipconfig but I'll start here.
Thank you,
Joy