FixWin doesn't actually look into your system and uncover problems. Instead, it lists several dozen potential problems in five categories: Windows Explorer, Internet & Connectivity, Windows Media, System Tools, and Additional Fixes. It lists all the problems you might have, not ones that it knows that you do have. So, for example, it lists "The Recycle Bin icon is missing from your desktop," even if the icon is there. You have to know you have a problem, and then use this program to fix it. It won't uncover problems for you.
Should you download the program? If Windows is working fine, there's no need to do it, because it won't do anything for you. But if you know that you have a problem, FixWin is worth the little download, in case it can fix it for you.