Just to add, the license you have for Office will be valid for both the 32 and 64 bit versions, however it's usually recommended to install the 32-bit version of Office as opposed to the 64-bit anyway. There are few benefits to installing the 64-bit version of Office, especially for the average home user, so even if you had both the 64 and 32 bit disks available I'd usually advise playing it safe and installing 32-bit anyway.
