At regular intervals, Shadow Copies makes copies of all of your documents and other files--think of it as taking a snapshot of sorts. There may be times when you have changed files, and want to revert to one of those older versions. The way you do it in Vista is non-intuitive, to say the least. With ShadowExplorer, you can easily look through all those old Shadow Copies, in a Windows Explorer-style interface, and restore any you'd like.
Note: After you install ShadowExplorer, you'll need to run the program as a system administrator or it will refuse to load.