I came back to the computer after a couple of hours and found that all the icons in the quick launch bar and 6 of them on the desktop, I have another 11, have changed to a square with a blue bar at the top with 3 stars and a Black arrow in the bottom left hand corner. Not knowing what had happened I used system restore but the only point for today was a entry that said Windows Defender checkpoint, that would not work so I went back to yesterday to a Software Distribution Service 2.0 point (what is this by the way?)which restored the computer but the 6 icons on the desktop remain changed and Windows Explorer on the quick launch bar remains changed.
I am running XP Home + SP2, Windows Defender, Spybot Search and Destroy, Spywareblaster, and Avast virus scanner. Why have the icons changed, seemingly of their own accord?