hi,lately my pc has been experiencing something weird,i can hear the HDD starts and shutdowns many times while the pc is on,and some times the pc gets stuck on windows loading screen and i cant here the hard rotating i shutdown the pc and wait for a sec and then start again i can hear it and every thing works fine,i tested the HDDs at a technician he said it's fine i thought it's an HDD problem but i also thought how could it be the 2 HDDs at once !,so what am thinking of now is the power supply,could it be the power supply ? and how do i know if it failed ?,thank you