For the screen grabs I used a piece of software called PrintScreen from Gadwin Systems. This is a piece of freeware that is just much better than the standard Windows Print Screen – you can capture sections of screens or whole screens very quickly – one grab after another.
I then used another freeware called iSpring to produce a Flash video from the PowerPoint.
I then used another piece of freeware called Camstudio to convert the Flash into AVI.
I have just realised that with some nimble keyboard fingerwork I can skip the iSpring stage and produce straight from PowerPoint to AVI using Camstudio. I expect this will give me better quality but will need to test.
For the sound, I wrote a script for a voiceover, then deceided against and put on a sountrack. I experimented a bit with different sound tracks suggested by YouTube and selected the one I thought worked the best.