The WUBI method is not the classic Dual Boot method which does need to create new, real partitions for Linux.
If you use WUBI, as far as I can tell, Ubuntu does not disturb or make a partition. WUBI and Ubuntu create a large file and that file encloses / fakes a Linux partition.
WUBI creates on the hard disk you specify, a folder
inside it is
\ubuntu\disks\boot\grub - which contains menu.lst
\ubuntu\install\ubuntu-8.04-desktop-blah.iso - this is the image - you can burn this to a CD using anything that burns ISO to CDs.
WUBI does make a few Windows entries:
a. it adds an entry to Add/Remove in Control Panel
b. it adds one line to the BOOT.INI file so that the Windows bootloader will execute that
c. it adds \wubildr.mbr - which is when Ubuntu / GRUB takes over the boot procedure once you use your arrow keys at the Windows bootloader prompt to choose Ubuntu.
d. it make the bunch of stuff in \ubuntu and subfolders.
Cleanup if you want to stop using Ubuntu appears relatively easy: the Add/Remove entry in Windows Control Panel will delete a, b, c, d.
The downside to the WUBI method is that you can't get rid of Windows if you fall in love with Ubuntu because the WUBI method does not create real partitions on your hard disk.