Vista - Laptop projector changes icon size

Does anyone know how to fix this? When we connect a projector to a notebook
running vista the icons zoom to the largest size possible and will not allow
you to change the size back (tried cntrl scroll, classic icon size etc...).
When I try to change things they do change for a split second then zoom right
back to the largest size. Also if I open a file, in excel for example, the
file gets zoomed the the largest percent.
We also just noticed that if you open windows explorer the icons are the
correct size until you click on one then they all get the zooming problem.

PS. System restore does fix the problem but need to know how to fix the
issue for presentations etc...

Thanks
Steve C