If you are on Vista and want to have the interface of Linux Ubuntu, then you could try Ubuntu transformation Pack which will transform your Windows Vista interface to the ubuntu interface .The transformation pack is available for Vista SP1 only. If you wish you can download it from the following link below:

Desktop Screenshot:

Transformation Pack Features:
1.) Boot logo
2.) Login screen
3.) Welcome Center
4.) PC-Properties
5.) Back and forward buttons
6.) Icons
7.) Wallpaper & Screensaver
8.) Rklauncher
9.) Sounds, Cursors & Spaces
10.) Visual Style for Vista

Download this transformation pack by using below link:

Download Linux Ubuntu Transformation pack for Windows Vista SP1 only

Also take a look @ Collection of best Transformation Packs for Windows XP & Vista Users