XP's 'briefcase' app is a simplified version of the file synchronizing method which is extremely easy to use. The concept of this application is a digital briefcase which can be moved from computer to computer via floppy or USB memory key (or on a laptop). It holds copies of all the user's current documents, and allows you to work on these files away from the computer on which they are based. Upon returning the briefcase to the original computer, you can update any files which have been changed.
So, when you are working on the same file in different locations, you have the issue of manually synchronizing the versions of the file so you do not end up with different copies in different places.
The briefcase can eliminate this problem by automatically synchronizing older copies of your files with the newer ones you have edited at home.
Note:The briefcase application will not work over a network. It can be copied over a network, meaning you can move the briefcase onto your laptop via a network, but the briefcase application itself will not update files over the same connection. Ultimately, the WinXP briefcase is most suitable for a single user who wishes to carry his or her files with them in an easily updateable form.
Check it out in File Synchronization
Overview - From the makers
How To Use the Briefcase Feature in Windows XP - Again, from the makers
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How to get "My Briefcase" in Windows XP