Desktop Not Showing

This is all new and I have neither added nor removed apps.

Win XP Pro. Boots up.

Desktop is totally vacant.

A service that shows a windows shows and runs properly.

The small microphone toolbar shows then goes away.

Glary window opens and asks if I want to upgrade. I click to close this.

ProcessExplorer (sysinternals) programmed to start but not seen.

Desktop is totally vacant.

No Start menu.

Desktop Right-Click does nothing.

Ctrl-Alt-Del brings up ProcessExplorer visible and running.

In ProcessExplorer I do a RunAs Explorer.exe an nothing happens.

In ProcessExplorer I do a RunAs MSCONFIG and MSCONFIG opens.

I fiddle in MSCONFIG and the desktop appears with icons.

That is about as far as i went, being exasperated at this point.

What's up ????

Suggestions please. I do have a Macrium boot disk and image (not clone)
backup before all this started but rather fix without reinstall.