FREE as in OPEN SOURCE!
Download and install Ubuntu 10.04 [5] and then simply apply the W7 theme [6].
And voila!
Source: http://lifehacker.com/5619064/w7-theme-for-ubuntu-brings-windows-7s-familiar-gui-to-linux [7]
Links:
[1] http://pulse.veltsos.com/category/it/software/software/os/linux
[2] http://pulse.veltsos.com/category/it/software/software/os/microsoft
[3] http://pulse.veltsos.com/category/it/open-source-foss
[4] http://pulse.veltsos.com/category/it/visualization
[5] http://www.ubuntu.com/desktop/get-ubuntu/download
[6] http://ubuntu.sun.ac.za/index.php?title=W7_Theme
[7] http://lifehacker.com/5619064/w7-theme-for-ubuntu-brings-windows-7s-familiar-gui-to-linux