What sort of disk? A CD-R is read only. You can always do a save as on the
other computer and save to its hard drive and make changes. Hope this helps.

To Expand on Rae's answer a little,

It sounds like your using a CD to copy yout presentation onto, this means
that you cannot change the file on the media directly as it is read only.
Your only option is to copy to a hard drive, network drive, USB key etc, and
edit that version instead.

Onr thing that catches many people out is that when the file is placed onto
the Cd it as 'Read Only' status set also, a property that is retained when it
is copied on to whichever re-writeable media you choose. You will need to
change this from your copy before you edit by right clicking the file,
selecting the Properties tab from the context menu and then removing the tick
from the Read Only attribute box.

HTH

Neil
www.nwarwick.co.uk