How to find out what this is? Video Problem?

Attached is an image displayed on my monitor. I recently bought a second monitor, and after installing and setting up this appeared on the No.2 (original) monitor. I think it is some sort of control box that does not display properly. Seen close up it has left /right arrows faintly visible. It only appears at the end of the boot process so there is a period where is is not there. I'm pretty certain it is some app/process that loads. Is there any way to find out which. It is not clickable.

Welcome
A clean boot should give the answer
http://support.microsoft.com/kb/929135

Thanks for the link. Followed instructions and disabling "Windows Event Log" removes the black box. I suspect it is some conflict with my ATI V4800 FirePro driver. I've seen other info on here about problems with ATI drivers and logging. This did not happen until I added 2 monitors to my system.
I figure I can live without the Windows event Log, but I'd really love to solve the conflict. I did load the latest ATI driver a week ago so I doubt there is an update quite yet.

What happens if you roll back the driver to the prior version?