You HAVE to do a clean install to change bitness. When you do the clean install a folder will be created in the root drive called windows.old. This contains the entire old OS (in your case Win 7 32 Bit). You can open this folder and grab all the data (pics, favs, music, etc) and move it to the new OS. You will also have to reinstall all your apps. Ensure that you have drivers for all devices in 64 Bit. (Win 7 does a great job of containing drivers for most devices).