Allow installation of Ubuntu on an existing NTFS partition

The Ubuntu installer could offer the possibility of installing onto an existing NTFS partition. This can be done by creating a single file on that NTFS partition large enough to hold the installation, formatting that file as an ext3 filesystem, and installing Ubuntu to that filesystem. Ubuntu can be booted by mounting the NTFS filesystem using the in-kernel driver (which allows writes to files but not reliable resizing) and loop-mounting the ext3 installation file as the root partition. Booting could be done via grub or via the live CD.

This would be very good for people who would like to try out Ubuntu beyond what is comfortable using the live CD, but who are afraid of repartitioning, or not yet decided. Booting from the live CD would mean that they do not even need to install a boot loader.