Though Wubi is only officially supported on Ubuntu Hardy Heron onwards (8.04), there is a trick exist which enables you to install Ubuntu 7.10 on Windows using a discontinued binary released by Wubi Installer project.
Read more at : Unofficial-Unsupported Tricks: Installing Ubuntu 7.10 Using Wubi though i couldnt find any reason to install 7.10, it is nice to know it could be done.