startup malware?

Am running windows XP on dell e6410 laptop.  Startup now takes forever and before anything is operable, two small windows show up in center of screen.  One asks me to down load a file or search for a program to run the file and the name of the file is something like STS6.tmp.  The second window right behind the first window shows a ghost like transfer going on from a globe icon to a ghost folder.  Clicking the cancel button makes both windows disappear and computer seems to function normally thereafter.  Switch users and the whole, long start-up process happens again, with a different ST**.tmp file name waiting to be downloaded or run.  Coincidentally when this first started yesterday, Norton would be listed as not active and afert some confusion, I downloaded NIS2012 (seems it was NIS2011 though I thought it had upgraded previously).  Anyone with similar annoyances or suggestions from the professionals at Norton would be appreciated.  Bob R