I downloaded the RTM (final) Windows 7 from Microsoft (TechNet Plus account) and had to make a choice whether I wanted 32 bit or 64 bit at the download site. You can download either or both and the same installation key applies to either version. Retail site downloads may be somewhat different. Perhaps you could re-visit the download site and check the site very carefully. You likely would have the opportunity to download the 64 bit version and use your existing installation key to wipe and install the 64 bit version. You are actually buying the installation key, not the DVD containing the OS itself. (Kinda like they give you the car, but you have to buy the key to get it started.)