I want to install Ubuntu in replace of Windows. I want to know if I can go back to Windows. If I decide this is not the right choice. I do not want to install Ubuntu side by side.
The best way is to make a separate partition in order to install Ubuntu. (you can do this with gparted (http://gparted.sourceforge.net/download.php). This method will not influence your Windows installation. At booting time you will able to make a choice with which operating system you want work.