Loss of disk space on Samsung external 1TB drive after 'clean up'

I know about the immediate 'loss' of disk space owing to the two different methods of measurement. 1Tb to 931Gb - it's annoying, but I'm used to it.

No, before a defrag by Fixbee I had 701Gb free, afterwards - in a matter of 2 hours - I had 537Gb. Obviously, I'm not going to use this product again, where a clean-up is obviosly a 'dirt up', but how do I undo the damage that it's caused - especially if it's not the only 'clean up' tool that might do this?

Thanks for the tip. I ran Windirstat and it found some of the missing space with 263Gb accounted for as opposed to 230Gb just before the Fixbee clean up. Windirstat found that this unaccounted for use was backup material. Windirstat, couldn't detect a further 182Gb of 'used' space. Unfortunately a neighbour intervened and took what would have have been my last resort. Cancelled backups in favour of manual backups, deleted existing backup files, export remaining files to another drive (in progress) and (to be done) reformat the Samsung drive. Even without the mystery space-eater I cannot afford the space taken by automated backups.

I say, unfortunately, because I'm sure I could have learnt something more from you and apologise for taking another course of action when you had only just started to help me. I of course still welcome any further comment.

Thank you - how can I limit the take up of space by shadows and stop them taking up such enormous amounts of space?

Out of interest, I just cut and pasted a swathe of files of my own material from the Samsung external hard drive to an internal drive and about a third of their contents have disappeared. The folders of the missing material have remained on the external drive and have been copied over to the internal drive, but on both sides the folders are empty or contain a tiny fraction of their contents - absolutely no sign of the moved material. Any ideas on how to recover the missing files?

I'm also beginning to wonder if there is some underlying problem of compatibility between Windows 7 and my Samsung external drive (the PC I am using is a Samsung RF511)

Thank you.

I went ahead with emptying the Samsung Hard Drive and 110 Gb were still missing as stated on the drive icon in My Computer. I ran WinDirStat again and it could only account for 16 Kb of mainly jpeg fragments. I formatted the disk and it returned to a sparkling 931Gb out of 931Gb. I don't intend to use this disk as backup or system restore again, nor use FixBee - ChkDsk and Defrag seem to cover what this application did, anyway.