Also like Ubuntu 9.04 you can install Ubuntu 9.10 in Wubi. There are two ways:
The one way is to make a backup of all important files and make a new install of Ubuntu. Then you can use the new Gnome version and you hard disk will be formated in ext4.
The other way is to update Ubuntu 9.04 via the update manager, but then you can't use the new gnome and your hard disk will stay formated in ext3.