Windows Volume Shadow Copy Service (aka VSS) is a rather clever low-level file backup feature that has been available in some form since Windows XP. In later Windows versions persistent shadow copies, with multiple versions of files, have been available. It's usually used by system utilities, such as System Restore and NTBackup, but a piece of software called Z-VSSCopy allows you to pretty easily access past VSS versions of a file you may have recently deleted, for example. In Windows 8, you can access previous/recently deleted file versions by using the file history feature - which also uses VSS.
BetaNews has a walk-through of using the tool here (the software is free for personal use).The most interesting option is probably "Show", which displays the contents of the currently-selected shadow copy in an Explorer-type tree view. If you've accidentally deleted a file on your desktop, say, you may be able to find a copy here; right-click it, select "Export" and the file will be restored to its original location. (You can only select one file at a time, though - no multi-select, and no folders.)