Thanks for this. Yes, I've looked at the Microsoft free training, which is great for learning particular tasks, though perhaps a bit fragmented for someone who wants to learn PowerPoint from scratch. I've bought a couple of books with CDs, which are good for beginners and intermediates. It's training for more advanced skills, like embedding flash video and using macros, that I'm finding difficult to source.
Any other thoughts would be really helpful.
An alternative to buying the DVD is to take out a subscription to the site which also grants you access to their literally thousands of hours of videos on all Adobe products. A lot of these videos can be previewed as well.
You can gain also get a free month's subscription when you buy an Adobe product. Without wanting to sound too much like a shill for the Lynda site, it has given me a lot of pointers to ways I can improve my own company's LMS and video content.