For the purpose of a lecture, refusal to advance to digital workflow is sheer Ludditism.
Call me a Luddite, but I found that the safest way is to prepare the "slides" on a computer and print them on letter sized tranparencies for overhead projectors. When something goes wrong with a lecture, it goes really wrong, like in having a blown fuse somewhere and no electricity to the power outlets. You can still salvage the lecture by handing out the transparencies to the audience and going to plan B lots of talk and drawings on the whiteboard. With Powerpoint you have a wide choice between
a) Blue Screen Of Death
b) Windows insisting that you have to (un)install some stupid network/printer/whatever driver before continuing and wants some OEM CDs inserted
c) pop-out messages all over the place, with warnings that you are low on system resources or disk space, and offering to close your active programs (Powerpoint) or delete your files in order to make more resources available
d) some X-rated screen saver starting out of the blue
e) your batteries going flat and you don't have the charger because the laptop said it had a full charge; in the rare event that you do have the charger, there is no extra unused power outlet where to plug that one too
f) XP detecting that too many hardware changes have happened and wanting you to phone Microsfot in order to get an authorisation number to continue
...and many many others
The Digital Age has come. Enjoy !
cheers, caveman
