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 will run on on all Windows versions from Windows 98 to Windows Vista, more platforms to come soon. 64-bit builds are possible but not yet available. Linux/*nix/*BSD are supported through Lubi, and Mac OSX will eventually be supported through Mubi (developers still needed).
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...
* Disabled windows downloader for Windows98