Excel 2003 - cells highlighted when move to another cell

[Excel highlight problems]

I am using Excel 2003. Not sure what happens, but when in Excel and move to
another cell, all cells in between are highlighted. I am not holding down
the left mouse button etc. so that the cells are highlighted. Once this
occurs, it affects every program in my computer. Normal functions take on
other properties.

Does anyone know what causes this and is there a patch to fix the problem?

 

[Ron de Bruin]

Maybe ?

Press F8 once
(extend selection)