If you are currently running a 32-bit version of Windows then you cannot upgrade directly to 64-bit Windows. Instead you will need to do a clean install of 64-bit Windows. If you purchased a retail version of Windows 7 or Windows 8, then a 64-bit version will be included; your key will unlock both. If your computer came with Windows 7 or Windows 8 already installed, on the other hand, then you may or may not have a 64-bit version as part of the restore and install discs that are typically included with your computer; check the discs that came with your computer or contact your computer's manufacturer to be sure. If you don't have this option, visit the Microsoft Store.