I have a folder "A", with 24 folders "B" under it, each of those 24 folders having anywhere from 1 to 21 folders "C" under it. Each of the final layer of folders (the "C" folders) contains anywhere between one and 26 files, for a total of 83 folders (84 counting the top level "A" folder) and 577 files.

In Windows Explorer, I carefully hovered the mouse over each of the "C" folders to get the size of the folder and entered the number of megabytes into an Excel spreadsheet and summed them. The total in the Excel sheet differs by about 2.5% from what I get if I hover the mouse over the "A" folder. (Excel says 28.2 GB, Windows says 27.5 GB.) While 2.5% isn't a lot, it still amounts to 700 megabytes, more disk space than my first four or five computers had -- COMBINED.

I know that the more files I have, the more partially empty sectors there will be, but I thought that hovering over the "C" folders would take that into account.

Why doesn't the sum of the individual "C" folders add up to the total shown for the "top" "A" folder in the tree?

tanstaafl.