32 and 64-bit refer to the operating system, not the file system. Files are not 32-bit and 64-bit. That said, backup your files BEFORE you upgrade. And do an in place upgrade as you will have to restore after the installation. See this note from MS website:
"If you want to move from a 32-bit version of Windows to a 64-bit version of Windows 7 or vice versa, you'll need to back up your files and choose the Custom option during Windows 7 installation. Then, you'll need to restore your files and reinstall your programs. For more information about performing a custom installation, see Installing and reinstalling Windows 7."