I have DETERMINED that my 3 year old quad core machine is 64 bit capable.  I know I can not upgrade from 32 bit to 64 bit (of course I have 3 Win 7 upgrade licenses).  I'd like to move to 64 bit.  Is there an economical way to do this?  Or MUST I simply BUY a full version of whatever flavor of 64 bit Win 7 I'd like?

I will appreciate any ADVICE or suggestions.Which Windows 7 do you have?
The lull retail package comes with both 32 and 64 bit.
If you have a OEM upgrade, you only get one flavor. 
I have Win 7 Home Premium.  My interest in switching to 64 bit relates to my belief that, with the 64 bit O/S, my three year old machine may perform somewhat better at VARIOUS functions involved in video editing.  If that were to prove to be correct, I could perhaps hold off one more year before moving to I7 technology.

At this point, it appears I'll have to buy a full 64 bit license, and do a clean install.  I have found no less expensive way to make the switch.That is exactly what you have to do, buy a new install cd and then do a clean or upgrade install.  I to had the same problem and searched for 6 months until i finally gave up and bought the dang cd.