Laptop with dual monitor, icons move when monitor unplugged

My setup:
Laptop Windows 7 Professional 64bit
Second stand alone monitor plugged into VGA port

While at work I use both the laptop monitor and the external.
I have the external setup to the left.
But have the laptop to the right as the primary with the icons and start bar.
When I shutdown, disconnect the laptop, then power back up at home only using the laptop screen.
All of my icons move to odd locations and some even become off the field of view.
My resolution never changes on the laptop screen so why do the icons move?

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