Quote Originally Posted by nick85 View Post
it's a button which becomes unpressed when you release it. when do i press that and for long (approximatively)?
The right order is:
unplug the mains cord
remove the battery
push the switch

Do you have the manual for your motherboard? Maybe it's in there how long you have to keep it pressed.
I have a motherboard where I can change the position of a small plug, I do that for several minutes to make sure all the power is gone and the reset function really works.