You are mixing things up.
1. If you change your mobo, your old systems will only be valid if you have a retail version. You will still have to upgrade a few drivers
and revalidate the OS. OEM versions will be obsolete.
2. If you install Windows 7 AFTER you changed your mobo, that is no problem. It will just validate with the new id. But you need to do a clean install.
3. All your programs you have to reinstall. Your Vista installations are of no use for Windows 7.
4. For your data you have a variety of options. a) you can create a seperate data partition under Vista and INCLUDE the folders into the Windows 7 libraries. And b) you can just backup your data and then put it into the Windows 7 folders.