I just observed the following.

Directory A contains 204 files matching particular search criteria, and
contains no subdirectories; I thus have an Explorer search results
window with 204 items.

Directory B contains seventy-odd files; a window is open on it.

The system is WinXP SP2, with an NTFS filesystem on a read/write volume
and I have full admin rights.

In the search results window I hit ctrl+A and verify that it has in fact
selected everything. (It also shows "204 objects selected" in the status
bar.) Then I right-drag and drop on directory B's window. It thinks for
a bit then spits up an overwrite prompt; some of the files have the same
names as files in directory B. I hit "yes to all". It continues to spin
and then ...

"193 objects selected". Deselecting shows only 193 objects in directory B.

No error messages occurred.

Now, my understanding is that there must be at least as many objects in
directory B as there were search results from directory A after this
procedure, for the following reasons:

* Having admin rights I can read and copy any file on this system. If
the file's in use or on a read-only medium such as CD-ROM I may of
course still not be able to alter the file, but I can read and copy
it.
* Assuming all of the files from directory A are copied successfully,
then 204 copies occur, given that I answered "yes to all" when
prompted whether to overwrite files. Otherwise, an error message must
occur.
* Since there are no subdirectories of directory A, no two of the search
results had the same name, so no file was copied and then later
overwritten by another file during the copying. Therefore, 204
distinct files with 204 distinct names should now exist in directory B
-- PLUS any files originally in directory B that had different names
from any of the results from directory A and were thus not
overwritten.

It follows from the above reasoning that either an error message occurs
or the number of files in directory B is greater than 203.

Since no error message occurred, we conclude that 193, the number of
files in directory B after the copy, is greater than 203.

Note also that nobody else was logged on to the same machine at the
time, nor were any autonomous processes concurrently deleting or
modifying any of the directories involved.

There can be only two conclusions: either Explorer fails to report some
errors, even ones fatal enough to possibly cause data loss (imagine I
*moved* the 204 files and ended up with 193!), or a state-of-the-art
computer is exceedingly bad at basic integer math.

Anyone know what the **** is going on around here?

--
http://www.gnu.org/philosophy/right-to-read.html
Palladium? Trusted Computing? DRM? Microsoft? Sauron.
"One ring to rule them all, one ring to find them
One ring to bring them all, and in the darkness bind them."