It's in 'control panel>folder options>general tab click on 'single click to open an item'
Alternative if you right click on an icon you can select 'pin to task bar' which will let you open with one click. I've got my most used ones there and not on the desk top, in fact you don't need any icons on your desk top unless you've an awful lot of programs you use a lot. I've got 21 icons pinned to the task bar, the rest I open from the start menu probably once a month.
Edited to add Re the mouse, have you tried going to the manufacturers site to look for a windows 7 driver for it? Or any other 5 button mouse by that maker which would probably work.
Last edited by green granite; 29th October 2011 at 16:21.