Hola Adrian, viendo la web de Microsoft (
http://windows.microsoft.com/en-us/windows/installing-reinstalling-windows#1TC=windows-7), lo que tienes que hacer es un backup de los datos, instalar el W7 a 64 bits y recuperar tus datos del backup.
The Custom option installs a new copy of Windows 7 on the partition you choose. This erases your files, programs, and settings.
Back up any files and settings you want to keep so that you can restore them after the installation is complete. You'll need to reinstall your programs, so make sure you have the installation discs and product keys for the programs you want to use in Windows 7, or setup files for any programs you downloaded from the Internet.
Espero que te sirva
