This is a new technology in Windows Server 2003 that did not exist in Windows 2000 Server. This technology is used to create a copy of the original volume at the time a backup is initiated. Data is then backed up from the shadow copy instead of the original volume. By doing this, all activity such as file changes, will not affect the backup, because it is using the shadow copy instead, which is not changed. So with this new feature users can access files during a backup, files are not skipped because they were in use, files open appears to be closed. You should use Volume Shadow Copy, but you can disable it. The only time when you want to disable it is when you don’t have enough free disk space. As you can imagine you need as much extra disk space as the file you will backup uses. This consumption of disk space is however temporarily and will be free when the backup is completed. If sufficient temporary disk space is not available Windows Server 2003 cannot complete shadow copy and the backup will skip open files.