Windows Explorer may show that a disk has plenty of disk space available. When you look at the same disk in Disk Management, you see that it is almost full. One thing that can cause this is leftover shadow copies. Some backup software will create a persistent shadow copy and after they have backed up the shadow copy to the designation, they fail to delete the original copy that is stored on the volume.
If you do not need these shadow copies, then there are two ways that you can delete them.
1. Use the VSSAdmin Delete Shadows command.
Example:
Vssadmin delete shadows /For=F:
2. In some cases, the shadow copies could not be deleted this way. In order to remove the shadow copies, you can set the maximum storage down to 300MB and Windows deleted the entries automatically.
Once you set the maximum to 300MB and click on OK, any shadow copies that are over 300MB will be removed from the drive and your drive space should be reclaimed.
Visit Technet Blogs for a nice detailed read!