Offline File and Folder Setup in Vista

” you’ve ever needed to access important files stored in a shared folder on your network but couldn’t because the network connection was unavailable, then you can understand the need for offline files. Using offline files, you can access files stored in shared network folders even when the network copies are unavailable. You can do this by choosing the network files you want to make available offline, which automatically creates a copy of the network files on your computer. These copies of network files that are stored on your computer are called offline files. Windows will automatically sync your offline files for you and open them whenever the network versions are unavailable.”

Goto to the windows help site
How to setup offline files in Vista