Problems transferring Word files over a network

[Rod]

I have a number of work files on one computer that when I
try to transfer to another computer over the network, it
says it cannot and gives me the message

Cannot copy XXXXXX: Access is denied.
Make sure the disk is not full or write-protected an that
the file is not currently in use.

I can copy most other word files but there are a small
number that will not transfer. Any idea why? I am using
XP Home.

The same thing happens with some image files.