when i got my macbook i planned on upgrading it to the max. I already have my 2gigs of ram, now for the HD. I dont need 120gb, im going for 100gb. I am pretty se on the 100gb hitachi travelstar 7200rpm. This will work ok, right? i heard about possible issues with them not fitting or w.e, i just want to make sure before i end 170 bucks.