Pop-up window in Windows Explorer

Whenever I go to C:\Documents & Settings\'my username' folder, I have a
"Sign In With Microsoft Passport Network" window open up. I can hit the
cancel button but it just re-opens a few seconds later. I can continue down
the path if I hit the cancel button and then the next folder (such as Local
Settings) quickly. It does not happen if I open any of the other folders in
Docs & Settings, only when I click on the 'my username' folder. Has anyone
had this happen? Am running XP SP2 with all updates current, AVG, and
Windows Defender. It's not a big deal but am curious what could be causing
it.
Thanks.



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