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.aspxNot broadcasting the SSIDhttp://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
