sounds like the bios battery is flat and needs changing
whats the make and exact model of the desktop
remove the wireless profiles and try and connect again
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How to remove Wireless Profiles - for XP
http://mgmcc.forumotion.net/networking-tutorials-f17/removing-an-existing-wireless-profile-t109.htm
- XP
http://mgmcc.forumotion.net/t109-removing-an-existing-wireless-profile
- delete the preferred networks
start> control panel> network connections> right click on the wireless connection> listed wireless networks tab in the preferred network list click on each one and - remove button
you will then have to enter the wireless security key for any networks you connect to - so make sure you know the correct password , and not using an incorrect password at all
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Remove the wireless security
Is your wireless security enabled?
if so - log into the router and remove the wireless security - now see if it will connect.
if it does - log back into the router and try with the wireless security enabled again
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