What I'm looking for is something small, light, and with a VERY long battery life - ideally at least 4-6 hours with minimal disk access, since I want to be able to leave a presentation running for several hours at sites where mains power isn't available. I want it to be capable of playing DVDs, and it needs to run a web browser, text editor, and Powerpoint. It also needs to be easily networked via cable or WiFi.
What I'm thinking of here is something like a Centrino machine running XP, or possibly something like an Apple Ibook G4 if that'll run the PC version of Powerpoint (or at least show PowerPoint stuff without me having to buy the software again).
I'm not in any huge hurry for this, it's a "want" item rather than a "need" item. And I'd be perfectly happy to go with an older machine or lower spec than the current maximums if the basic needs above are met. So... any suggestions, or anyone know of anything going really cheap?