The latest update (08/11/2006) of the SSD detections reports the presence of Windows.Explorer as a possible threat on my Windows XP Home SP2 system, running SSD 1.4. The Registry key value involved is alleged to control display of the "Log Off" button on the Start menu. On my system, this value has no effect whatever! It can be altered, for example, by TweakUI, but there is still no effect. Neither 0 (show) not 1 (hide) affect that button. There was a flurry about this detection several months ago referring to it in the context of a beta version of SSD, but it has only just appeared in the stable version today. I have marked it to be ignored in future on my system.
Incidentally, the button can be controlled in a very similar way using a different value in the same key