Please, I have Windows 7 on a 265 GB Samsung 850 Pro which Windows Disk Manager intially shows 29 GB used space of a 67 GB partition. The only other partition is an empty 141 GB. Every time I populate this second empty partition the first partition shows only 5 (five) GB of unused space remaining. Any disk usage software such as Glary or Treesize does not account for the increased space usage which Windows Disk Manager or Explorer show. In fact, they show no disk space shrinkage. The OS on the first partition is a clone made by Macrium Reflect v.6 of a 56 GB OCZ Vertex 2. Rollback Rx Professional that I've used for several years without any partition problems is installed to this first partition. The second partition is not a partition protected by Rollback. The snapshots space Rollback occupies is less than 6 GB. Also, without additional snapshots no additional use of space incurrs. I don't understand the geometry, algorithm, whatever . . . particular to this situation. I do know that having 141 GB that could be used, but is not used is a waste of GBs and $$. Without a second partition, of course, backing up the OS partition with substantial addition of files to it takes considerably more time and space.