to upgrade to max of 8gb I need to fit 4 x2gb 240 pin ddr3 1.5v 1333 speed cards. yesterday while spending the day with my son he gave me 4 cards which he had spare, which match my spec except that the voltage is 1.6 instead of 1.5 and the speed is 1600 and not 1333. my son who works in IT thinks that they will work but just slightly slower. what I want to know, is he correct, or will I harm my pc by fitting these cards. I need to know this before I start because I have to move a lot of stuff to be able to disconnect my tower unit and then fit the ram, and I do not want to waste time etc. if anybody can help me with this it would be most appreciated, as I do not want to wait until start of jan before I can ring somebody, after there exmas break.