Where has my desktop gone

I turned on my PC this a.m. and all I get is a Windows Explorer screen (everything seems to be working except I can't see it. What's loading Explorer - it's not in startup nor is it shown in startup processes

I get the same result in Safe Mode

I assuming my PC has been nobbled - what have I got to do to at least see a desktop again

(I am using another PC to send this - mine is a Dell Dimension L800r running W2000)