It sounds to me eather you got bad ram or there is a compatibility issue with the (type / speed) most computers / labtops will go black screen when there is a memory issue.

put the old memory bac in it as it was. if it boots fine then you have mamory that is not compatable. does the screen even flicker or shoe the BIOS? if you get no reaction from the screen (After you put the old memory back in) then the screen has gone bad.