Theoretically, however, as with Excel and Word, I believe the ppt will be
opened read-only by subsequent users.
If you're just looking at making a presentation /viewable/ by simultaneous
users, consider changing the filename to a PPS file, which will autorun the
presentation in slideshow mode.
Additional questions about Powerpoint usage would be better directed to the
Powerpoint communities, rather than this Office /Update/ community.