since 32 bits and 64 bits don't really have the same file needed, you cannot perform an upgrade. But you can do a clean install with an upgrade disk. All you have to do is to backup all of your personnal data. And since Win7 don't have a mail program, you will need to download windows live mail, and use it to transfer you email to it.
Once done, insert the upgrade disk, let it run, but don't choose upgrade, choose the other option. This will create a Windows.old folder with your vista in it and Windows 7 will be installed. This procedure don't format the drive.
If you format the drive, then decide to use an upgrade disk to clean install, it will work but you'll be warned that you cannot use this key on a full install, only for an upgrade. At this point, you have two option. you can try updating you new Windows7 or simply take 30 seconds to modify a registry key and validate your clean install as an upgrade. I would use google to find the way you want.