Puppy Linux and Ubuntu 12.04
Thanks to both of you for your replies.
I checked out the Puppy Linux site, the OS is nice and little. DSL Linux is even smaller, but I don't know if it will run as a LiveCD, or automatically install.
Unfortunately, I don't have access to Nero, just the default Windows Disc Image Burner, so it probably won't let me burn larger than 700MB.
I guess there's no getting around that hard drive!