XP SP1 explorer.exe fails on start up (every time)

Archived from groups: microsoft.public.windowsxp.perform_maintain (More info?)

Help!!

My friends computer fails on start-up with an
explorer.exe error (XP SP1). The desktop background is
shown but there are no icons/taskbar. Some applications
can be run from task manager but these are limited.

Have scanned for virus/trojans on symantec & trend micro
but non found. Once scanned - did a clean boot but error
remained upon start-up. Have also restored to a known
good configuration, but the error is still there upon
start-up.

I am now unsure of what action to take in order to
resolve this issue/problem.