I purchased Windows 7 Home Premium as part of a supplied computer system approx. 2 years ago. The OS package contained two disks, one to install W7 32 bit & the other W7 64 bit. I installed the 32 bit OS but now are considering installing the 64 bit OS. Is it permissable to uninstall the 32 bit system & install the 64 bit in its place or must I purchase another W7 OS? It appears there is only one product key for both. I attempted to contact Microsoft by email but, after this length of time, the activation number I was requested to submit had apparently expired.