Are you referring to Windows? If so, then it depends on the version. OEM Windows will need a new key. Some editions of retail Windows will need a new key, some will not. However, please be aware that you might run into problems getting drivers for your laptop if the manufacturer doesn't have 64 bit drivers available for some of its hardware. Do you have a need to change it to 64 bit (assuming I am understanding properly and it is Windows you are referring to)?