File copy errors

[Steve]

After running defrag on my kid's computer, I can't seem
to share/copy/move some files from a shared drive from
one computer to the next. I've tried reboots, removing &
reactivating sharing and trying each from both computers.
This problem not only plagues some of the files that were
already on my kid's computer, but one's I was able to
move over to his computer afterwards. Everything was
working perfectly fine till I defragged his machine. The
error(s) I get are, "The file isn't in the specified
folder", "is in use", "can't find file" and that I
haven't gotten permission to move/copy/view the specified
file. Again, this happened even after I just moved a file
over to his machine to burn it to a CD. It moved over
fine, but when I tried to move/copy it back, I couldn't
do so.

As I said earlier, everything worked fine before the
defrag. I can't see any thing that defrag changed in my
kid's network settings... that I've noticed or was
obvious to me. We're both running WinXP. Mine is Pro, his
is Home. All hot-fixes & Updates, DX9b blah, blah, blah.
Perhaps I'm overlooking something simple, but I need to
be prodded into the correct direction... I hope.

Thanks in advance.