The ProgramData folder, which first appeared in Vista, is the old "AllUsers" profile, which you were accustomed to in XP.
Many programs save settings and backups in that folder. Several third party applications are being installed (improperly) there instead of to the Program Files folder to bypass the permissions issues. Updates to antvirus programs and others usually go there, also.
I would suggest it is the updates to some of the previously installed programs, that you are seeing. None could give you safe advise on this, but, if you want to clear out programs that you are positive no longer exists, I would suggest you backup or copy them somewhere where you can easily reference them to replace, should you create a pending OS failure.
Sure it would. But perhaps I do not follow you? If you are going to reinstall, why trouble yourself with removing them in the first place? If they are not in use, they are not using any rsourcs - merely using disk space, which we mostly have far in excess of requirements.
Program Data is a hidden file Windows 7 uses for application files an important information. Unless you have specifically requested to hide a file, please consider all hidden files to be applicable and necessary to optimum system performance.
Should you require additional assistance and guidance, Microsoft does have an official Windows 7 Support Forum located here http://tinyurl.com/9fhdl5 . It is supported by product specialists as well as engineers and support teams.