Hi all.  I have a puzzle, well it is a puzzle to me, it might not be so for many of you.

I have 3 28tb external hard drives.  When I buy and download my music I gather them together then move them to the drive I've labelled M1.  When that has been done I then copy them to the other two drives.  I've just finished this morning copying from m1 to m3 then I delete any duplications and empty the recycle bin. While inside both drives I do a property check to be sure all files had been transferred and the file number and total size matched on both drives.  By  chance I went to "my computer" and found m1 and m3 but did not open them but did a property check.  M1 said the used space was 16.4tb.  However when I checked m3 it said the used space was 20tb, why the discrepancy?  Both drives have the same number of files, both drives have had their recycle bins emptied and I did a disc check on m3 and there were no issues.  Somehow windows is seeing files that are not there.  I'm not concerned about this as I will at some point reformat m2 and m3 and copy from m1 but I am just curious just how there is such a difference of 3.6tb and by the way, that 3.6tb is roughly the size of the duplicated files I deleted.  Now I've restarted the computer, I even shut it down and re-booted it and even changed to a different computer and I still get 20tb.  Anybody got an answer?  Walter.