Question : Problem: Cannot see WLAN when SSID not broadcast

I had setup my WLAN at home w/ a non-broadcast SSID, and WPA encryption.  Everything had been running fine for months when suddenly 1 of the 3 pcs on the network could no longer see the WLAN.  I added a Linksys usb-g adapter to the PC hoping it might be my PCI adapter, but no luck.  I reset the router to factory default, and could then see the network.  Once I stop broadcasting the SSID, the PC is no longer able to see even the "Unnamed" network.  I'm stumped.  

Answer : Problem: Cannot see WLAN when SSID not broadcast

The "Unnamed Network" bit - isn't that only Vista that display that phrase?  Or are you using the Linksys software for making the connection to your wireless network?

Do you have the wireless PCI adapter still installed when you added the USB wireless?  Did you also uninstall the wireless  PCI adapter software?  Perhaps a "clean start" with everything (software & hardware) uninstalled can help troubleshoot the issue...

Also, just curious, do you already have this installed?  

The Wi-Fi Protected Access 2(WPA2)/Wireless Provisioning Services Information Element (WPS IE)update for Windows XP with Service Pack 2 is available
http://support.microsoft.com/?id=893357

I am not sure of your entire setup, but it's intro says it all:

The Wi-Fi Protected Access 2 (WPA2)/Wireless Provisioning Services Information Element (WPS IE) Update for computers that are running Microsoft Windows XP with Service Pack 2 (SP2) is available. This update enhances the Windows XP wireless client software with support for the new Wi-Fi Alliance certification for wireless security. The update also makes it easier to connect to secure public spaces that are equipped with wireless Internet access. These locations are otherwise known as "Wi-Fi hotspots."



Also, here's some additional reference material (why I no longer use the "do not broadcast SSID" feature) :

Why Non-broadcast Networks are not a Security Feature
http://technet.microsoft.com/en-us/library/bb726942.aspx

Not broadcasting the SSID
http://en.wikipedia.org/wiki/SSID#cite_note-0

Myth vs. reality: Wireless SSIDs
http://blogs.technet.com/steriley/archive/2007/10/16/myth-vs-reality-wireless-ssids.aspx