Honestly, if you went for backing up the documents, mails etc. and reinstalled the whole **** computer, it would take MUCH less time than figuring out which mess is which And in fact, if it got to such point to have enormous amounts of crap in for example the installer folder, it's apparently time for a reinstall anyway! I would make a list of what's in the start menu and then just run all of the .msi files in each of the folders in installer one, seeing which is no longer used. Windows have a bad habit of keeping everything... And the hotfix backup folders in root of \windows are absolutely safe to delete.