I just installed a new 320gb western digital HD in my macbook and now when I turn the machine on it just does not switch on. I checked the ram, I checked the HD seating and the L-Bracket but still no luck. Took out the battery / power cord to reset the power. I also had a go at doing cntrl-mac key-power and no luck. I believe that the macbook supports 1.5gs Sata but most drives can switch back to this - if there is an issue with this would it cause the macbook not to switch on at all? I don't think SATA drives have jumpers do they?