Not many people are aware of this nice little feature in Microsoft Word 2002 and above, simply called Version. It can be found under File>Version menu. When turned on, it automatically keep tracks of each “save” you make to the word file and enables you to retrieve the previous version of the file. All versions of the file are stored within one document so you don’t have your hard disk cluttered with different versions of the same file. Windows will show only one document when viewed from Explorer, and when opened it will open the latest version. The previous versions of the word file are available through the Version menu. For each version, Word records the date and time when the version was saved making easy retrieval.
If you want to extend this feature to other files as well, then there is a Yahoo widget called Versionator. All you need to do is drag a file or folder to the Versionator’s window and it will automatically save it with the date, time and a comment. You can retrieve the file later.