Gosh visual props for a talk on viruses is a tall order without a computer.
If you want to catch your audience's interest there are a few old historical viruses that are fascinating.
Cascade was the famous one 15 years or so ago where the letters "fell off of your screen"
http://www.borg-perg.asn-linz.ac.at/informatik /viren1/Cascade.gif
Could you rig up something like this with scrabble tiles collapsing?
Then there was "casino" if your machine was infected it would offer you the chance to play cards. If you switched off your machine would be trashed as it would if you lost .
These are pretty much extinct now but always grab an audience.
Also worth mentioning virus hoaxes. (pen pals, Jesus loves you, Good times) These always follow the same pattern "Today X (usually Microsoft) have announced a new virus that cannot be detected, does (all sorts of appalling things) tell everybody you know"
Before you know it you are getting dozens of e-mails from everyone telling to switch off your lights and sit in the dark in case this nasty virus gets you.
Kind of a virus without a virus sort of thing