I can't get a straight answer on this, and please DO NOT close this question and redirect to the endless other questions which also provide unclear answers. I'm looking for a yes or a no.
From microsoft FAQ :
You cannot upgrade from a 32-bit OS to a 64-bit OS or vice versa. You will have to backup data, clean install and then reinstall the software apps that you are going to use.
Keys are architecture neutral, the same key will activate either 32 bit or 64 bit but you can only use it once.