Are you talking about the normal security in windows xp sp2 , if its that goto start > run > type "services.msc" without quotes.
Scroll down the list , find "Security Center" , right click > goto properties > Click Stop and in startup option choose disable if stopping it doesnt solve your issue , when you finish your transfer and watch the file undo above and restart the service. Hope this helps. If this is not related to your issue disregard it