My sister's macbook pro's hdd just failed and I was planning on upgrading mine into a larger one anyways so I'm going to switch my hdd into hers. But what I am wondering is if I have to reformat the hdd or anything, can I just switch my hdd into her laptop and everything would start up and all the programs would run normally? If that is the case, would my serial number show up on her laptop? Because in the future, if there's any problem with her laptop and she had to bring it to the apple store, I don't want the people giving her trouble for having different serial numbers on the hdd and the physical serial number on the case. If the serial numbers are indeed saved on the hdd, would I actually have to reinstall leopard using her recovery disc to get the serial number right back into the hdd so that it shows up in the system profiler? Or would the serial number "change" itself once it realize its not running on the same laptop? Hope this makes sense to you!