I recently bought a copy of Windows Ultimate OEM 32 - without stupidly realising until it was too late that it was the 32bit version. Is there any way I can upgrade this to the 64 version?
No way that you will want to hear. You could install it and then buy the upgrade version and get the 64 bit. Somehow, I don't think that is what you had in mind.
there's no problem. just go to www.windowsvista.com/1045/OrderMedia and order 64-bit DVD or CD. U'll pay only for ship. U can use 32 or 64 version and the keycode is same. it's legal. greetings