right-click the "Start" button, and then click "Properties".

on the "Start Menu" tab, click "Start" menu, and then click "Customize".

on the "Advanced" tab, uncheck the "List my most recently opened documents" box.

the next time you click "Start", the "My Recent Documents" folder is not on the "Start" menu.

to empty:
on the "Advanced" tab, click "Clear List" to empty the "My Recent Documents" folder.

it is somewhat difficult and not recommended if u wanna totally disable the function.