Resolved Wireless Network/No connectivity

Hi everyone,
I'm having a problem connecting to my wireless home network. The problem started after I changed the default password on my wireless router (Linksys WRT45G) in order to easier connect a new wireless printer to the network. After changing the password, my computer (older HP laptop, running WinXP with Avast virus protection and Windows firewall) would not connect to the internet. When the Wireless Network Connection 2 page is opened, it shows my network name(SSID), Speed at 54Mbps, Signal Strength: Excellent, Status: Limited or No Connectivity. I then connected the computer through an ethernet cable and switched to the LAN connection. I was then able to connect to the internet and went to the routers web page. It showed that the wireless status was connected and broadcasting IP adresses. I then went to the website for my AT&T DSL modem (Speedstream 5100B) and its status showed it was connected and working properly. Still unable to connect wirelessly.
I then started researching what could be wrong, checking everything from viruses or malware, to registry errors, to resetting the winsock, to resetting the router, deleting the software and reinstalling it from the DVD 5 separate times. I've gone through every list I could find, and many websites such as PCHell, Major Geeks, CNET, and Microsoft. I've tried several utilities, but still no luck. I'm at the point where I can't think of anything else to do. If anyone has any ideas to try, I would really appreciate it. If no new ideas, I would appreciate someone either telling me or linking me to a way to reset my XP wireless network settings without deleting my wired internet access settings, and I'll try starting over again. Thanks in advance for any help, links, suggestions, or encouragement.

 

There should be a little recessed button on the back of the router that you can use to reset it to factory defaults.

 

Thank you TonyT,

I followed your instructions, with one addition, (instead of entering the new password, I entered the new encryption key) because I had tried this before (entering the new password) and it didn't work. When I came to the wireless page in order to reset the "preferred network" list, the spot to enter the new SSID and password was highlighted, and something just told me to click off the "security code is provided for me" box. I got to the enter and reenter boxes for the codes, entered them, clicked OK, and I was connected to my WIFI network again.
Thanks again for responding, and the advice