Wow, I just was searching google for ubuntu vs windows and ran across this application that installs Ubuntu right on top of windows, yea I think its pretty lame to install a Powerful operating system such as Ubuntu on top of windows which is slow/bloated as hell but it is possible.
From the site
Wubi is an unofficial Ubuntu installer for Windows users that will bring you into the Linux world with a single click. Wubi allows you to install and uninstall Ubuntu as any other application. If you heard about Linux and Ubuntu, if you wanted to try them but you were afraid, this is for you.
Wubi is Safe
It does not require you to modify the partitions of your PC, or to use a different bootloader.
Wubi is Simple
Just run the installer, no need to burn a CD.
Wubi is Discrete
Wubi keeps most of the files in one folder, and If you do not like, you can simply uninstall it.
Wubi is Free
Wubi (like Ubuntu) is free as in beer and as in freedom. You will get this part later on, the important thing now is that it cost absolutely nothing, it is our gift to you...
How does Wubi work?
Wubi adds an entry to the Windows boot menu which allows you to run Linux. Ubuntu is installed within a file in the windows file system (c:\wubi\disks\system.virtual.disk), this file is seen by Linux as a real hard disk.
Is this running Ubuntu within a virtual environment or something similar?
No. This is a real installation, the only difference is that Ubuntu is installed within a file as opposed to being installed within its own partition. Thus we spare you the trouble to create a free partition for Ubuntu. And we spare you the trouble to have to burn a CD-Rom.
This istaller installs Ubuntu on a loopback file system located on your Windows partition, while making it bootable just like a real-deal Ubuntu install. In fact, it _is_ a real-deal Ubuntu install, albeit in a slightly unconventional manner. If you go glassy eyed at the word "loopback", don't worry.. it's just a fancy way of saying that your whole Ubuntu install is self-contained and stored in a single large file on your Windows drive.
Grab a copy of Wubi Here