Wubi is an officially supported Ubuntu installer for Windows users that can bring you to the Linux world with a single click. Wubi allows you to install and uninstall Ubuntu as any other Windows application, in a simple and safe way. No need to burn a CD, just run the installer, enter a password for the new account, and click Install. Wubi will download and prepare the required files, and ask you to reboot in order to complete the installation. You keep Windows as it is, Wubi only adds an extra option to boot into Ubuntu.

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Wubi does not require you to modify the partitions of your PC, or to use a different bootloader, and does not install special drivers. Wubi keeps most of the files in one folder, and if you do not like it, you can simply uninstall it as any other application.
Wubi is Simple
No need to burn a CD. Just run the installer, enter a password for the new account, and click “Install”, go grab a coffee, and when you are back, Ubuntu will be ready for you.
Wubi is Safe
You keep Windows as it is, Wubi only adds an extra option to boot into Ubuntu. Wubi does not require you to modify the partitions of your PC, or to use a different bootloader, and does not install special drivers. It works just like any other application. Wubi is spyware and malware free, and being open source, anyone can verify that.
Wubi is Discrete
Wubi keeps most of the files in one folder, and if you do not like it, you can simply uninstall it as any other application.
Wubi is Free
Wubi and Ubuntu cost absolutely nothing (free as in beer), but yet provide a state of the art, fully functional, operating system that does not require any activation and does not impose any restriction on its use (free as in freedom).
Download wubi here

Windows 7 Tip: 





I have a WUBI installed Ubuntu. Can I just do the same to upgrade to the new 9 version? I mean use WUBI and download the new version right on top of the old one? Or must I delete the entire old version????