Mother Board serial number changed

It's fine - they will have a record of your changed serial number. It's normal for a logic board replacement to change (or remove) the electronic record of the serial number (but it's also physically printed on/in the MBP).

Hi Imran,

Are we referring to the MAC address or the actual serial number? If we're referring to the MAC address then absolutely to be expected. If we're referring to the serial number that's being displayed in System Profiler (and read off the MLB) then that's absolutely not to be expected.

I had my iMac's logic board replaced by one of Applecare's onsite technicians a few months back and the part comes with a "blank" serial number. That is to say... none. After he performed the installation and verified that the part was functioning correctly and my issue resolved he inserted a CD, started up off the CD and "zapped" my logic board with the serial number of my computer. He stated to me that this was the process of all the logic boards that he services (including portable computers at his repair shop). Apple gives him some CD to make this happen, so it's easier for the customer to read off their serial number then to look for it on the machine.

With that being said, you shouldn't have a "new" serial number. If anything it'd be blank. So based on my personal experience and the feedback from the repair technician I don't think the serial number is correct. I certainly don't think asking for a new machine is the answer, however, more just for them to properly identify your hardware serial number to the logic board.

Your new logic board should have been re-serialized with your original serial number when it was replaced. Sadly, that step is frequently overlooked by Apple Certified Repair Centers. I've had to go back for 3 out of four main logic board replacements.

As has been mentioned, they "can" burn the correct serial number into the ROM of the new board. From what I understand, this can only be done once. The most common thing I have seen is for the to just skip this... but I have seen reports of people having the wrong number. Provided you have had your service done by Apple (as you have indicated), it shouldn't be an issue regardless. They'll have a record of it. Just to put your mind at rest however, just give them a call and explain your situation to them and they should be able to let you know for sure.