pass word in the administrator

pass word in the administrator

hi I have 2 dell lap tops that I have not used for a long time and when I swiched them on so to give a good check and update the admin pass word page came on and as I do not know the said pass words I cannot get pass it. Even when swiched on and try to open in safe mode or F2,F8 and F12 it will not let me pass is thir any way round this problem.