While Windows XP does not enable automatic non-preferred connections by default, some users enable it in an attempt to simplify connecting to their own home network. Users should instead configure these as Windows XP Preferred networks which allows automatic connection to the home equipment yet still prevents auto-connection to other networks.
from here
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these may help , read through them, I do not use a wifi connection so am not sure, but searched through several pages of articles and threads to see if I could find your exact issue. The ones below seem to be about network dropping, and I do not know if that is the same as network switching.
http://www.werockyourweb.com/your-wireless-connection-dropping/
http://www.tp-link.us/article/?faqid=186
Windows XP periodically checks for new available networks. If it finds a new network listed higher in the Preferred set that is enabled for auto-configuration, Windows XP will automatically disconnect you from the lesser-preferred network and re-connect you to the more preferred one.
I am not sure , how I read it is that if this setting is ENABLED then it will look and connect to non-preferred networks, it would appear that this should be DISABLED.
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from here
As I understand it you seem to have several listings and if a preferred network is higher preferred it will switch to it, maybe you should delete all the preferred networks except the one you want it to stay connected to.
is it working now??
do you have windows handling the connection or through your wifi manufacturer??
it is best to have windows connect you.
https://www.microsoft.com/resources...ocs/en-us/wlan_client_configure.mspx?mfr=true