Off-line Access to Shared Folders (caching)
To make shared folders available offline, copies of the files are stored in a reserved portion of disk space on your computer called a cache.
Since the cache is on your hard disk, the computer can access this cache regardless of whether it is connected to the network. By default, the cache size is set to 10 percent of the available disk space.
You can change the size of the cache on the Offline Files tab of the Folder Options dialog box. You can also see how much space the cache is using by opening the Offline Files folder and clicking Properties on the File menu.