1. Original Equipment Manufacturer (OEM) Activation is also known as OA. It basically is OEM basic input/output system (BIOS) activation — meaning they’ve activated it already and you don’t need to enter the key and activate yourself.
2. You will only be able to activate one copy of Windows 7 with the product key number being used for either the 32 bit or 64 bit version at one time, not with both. It will only allow for one installed copy with it to be activated. If you try to do it on both 32/64 bit versions, you will probably get the Your Product Key is already in use or The Windows 7 product key you typed is invalid for activation message.