NEW! Mini ISO-CD Download (needs high-speed Internet access: installation starts on CD and uses Internet to complete)
IIRC you can do a basic desktop with just the first disk, but it's usually best to get all 3. I can't remember if the installer's individual package selection allows you to see which disk something's on, though I know there's a prompt to ignore using a cd if you dont have it. I've only ever done installs with the complete set of disks (usually buy all 4 for about £9).