With Windows XP you can. It always puts its bootloader and config data on C:, so if you install it to D:, they're separate. With Vista, it sees the drive its on as C: always, so it's not quite the same, but it's not hard to remove secondary OSs.
Not really. All you have to do is format the drive/partition its on, then remove it from the bootloader. Maybe its different for Linux though. :biggrin: