MyBook 1.5tb space problem

WD External and Portable SSD External SSD for Windows
1

I have two 1.tb mybook drives, i copy 1 to the other as a backup, yet for some reason 1 has less space then the other. i checked for hidden files yet i dont see anything. can someone help?

also anyone know of any software to mirror the harddrives so when i put something on 1 it copys to the other?

2

How much of a difference is there? Maybe something like SyncToy http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=15155 would work.

Joe

3

5GB’s and to me thats a bigg difference. so id like to know whats going on.
When i select all the folders together the information is exactly the same.
yet when i look under my computer theres a 5gb difference bettween them. yet i see no hidden files or folders. so i cant figure out whats up.