under p>XP system, open the control panel-folder options-view-display all files-OK, and view the partition disks one by one (usually in the last partition disk). If you can see a hidden folder about 611M, it means that this system has been backed up. Open the computer under win7 system-Tools-Folder Options-followed by the same operation as XP, but the folder size is generally around 3-4G.