Cannot open or delete data files !

When trying to open or copy my data files and documents I receive error
messages for many of those files and the operation aborts. Some examples of
the error messages we receive are as follows:

COPYING FILES: ( The disk is not full or write-protected and the files are
not in use )
"Cannot copy 'FILENAME' : Access is denied. Make sure the disk is not full
or write-protected and that the file is not currently in use."

ACCESSING THE SECURITY TAB FOR THE FILES:
"You do not have permission to view or edit the current permission settings
for 'FILENAME,' but you can take ownership or change auditing settings."

OPENING FILES IN WORDPERFECT: ( The files are not marked as read-only and
are not in use )
This document ('DRIVE, PATH, FILENAME') is in use or is specified as
read-only. You may edit the document, but you must save it with a new name.
Continue?"

In our best estimation there is a problem with the permissions, but taking
ownership of the top-level folder or certain individual files does not seem
to alleviate the problem. How do we take ownership of ALL the files and
folders? What other considerations may be preventing us from opening or
copying these files? Note that it appears we CAN delete the files, just not
open or copy them?

We would sincerly appreciate any help someone might have, this is a serious
problem preventing us from backing up or recovery our data files on this
drive.

Thanks