Bootcamp Support Software 5.0
The version of the Boot Camp Support Software depends only on the model/year of your Mac and the version Windows you are trying to install. When installing Windows 7, you should only use the Boot Camp Support software given at this Apple website. The only exception would be if this site did not provide a download for your model/year Mac.

Note: According to Apple, Windows 7 should include Service Pack 1 (SP1). Although, some users have posted success without SP1.

Once the Boot Camp Support Software is installed, you can run Apple Update to see if any updates are available. Unfortunately, the Apple Update, installed by some of the older Boot Camp Support Software versions, is no longer supported by the Apple servers. However, if you install iTunes or iCloud, you will get a newer working version of the Apple Update software. Whether this version will provide Boot Camp software updates is questionable.