If your PC has a 64 bit-capable processor (CPU), you can install a 64-bit version of Windows 7, even if you are currently running a 32-bit version. However, to install a 64-bit version of Windows 7 on a computer already running a 32-bit version, you'll need to back up your files and choose the Custom option during installation. Then, you'll need to restore your files and reinstall your programs.