Slow opening Windows and Internet Explorer

About a week ago i noticed that when i opened windows explorer, there was a delay. I thought nothing of it at the time, probably just a gremlin hang but now it is constant. Everytime i open a windows or internet explorer window, there is an 8 second delay (before it was instantaneous). I am running Service pack 2 on an Intel 3.20GHz machine with 3.5 gig of ram. I have run Bit Defender online scanner, Spysweeper and Adaware SE and the problem persists. Any suggestions??