I have created few files in excel 2003 and restricted the permission to
access via Information Rights management (IRM).

Recently, i was temporarily working on a colleague's pc and wanted to access
the same files. On opening, I was asked that I should obtain permission to
open these files. I followed the process and could do the work successfully.
Later my work was over on that particular pc so i wanted to remove the
acccess rights given to it earlier to access the files. But i was unable to
do so.

Can please someone guide me with the process of removing IRM from a
paticular PC or Windows.