Q:
A: Yes, it will weigh exactly the same because inside there are rapidly spinning disks called platters that hold all the information magnetically. Information is stored by the polarity of different tiny sections of the hard drive, and is altered by the read/write head which is a small electromagnet that is on an actuator arm which controls the position of the read/write head. When the hard drive gets "written on" the read write head simply alters the polarity of the millions of different little sections on different parts of the hard drive. This is the main reason why they say magnets and computers don't mix, magnets can destroy carefully arranged data on a hard drive, however modern hard drives are encased in a Faraday cage that resists outside electo-magnetic interference. So when you write on a hard drive you don't really "Write" on it, you rearrange things on it, and because of that you don't change its mass.