Some of the Windows users that want to give Ubuntu Linux a try and don't want to give up their Windows system can always choose to have them both in the
same machine. And this also applies for people that need both Windows and
Linux on the same PC for business purposes. A dual boot machine has either multiple hard disks or multiple hard disk partitions, with each partition or drive containing an operating system. Now there are different methods to achieve a correct dual boot system, it's your decision which one you want to give it a try.
Method 1: The easy way
You can choose the brand new Ubuntu Installer for Windows machines. The aim of this installer is to provide an easier way for a Windows user to install Ubuntu Linux without having to know how to repartition the disks or to set up a multiboot system.
Note: With this installer, you can also choose to install Kubuntu (Ubuntu with KDE desktop) or Xubuntu (Ubuntu with XFCE desktop).
Method 2: The hard way
1. Make sure your Windows partition is defragmented and backup any important data.
2. Boot from the Ubuntu Desktop CD, double click on the Install icon on the desktop and follow the normal installation instructions. When you arrive at the Partitioning screen, select the option that let's you resize IDE1 master, partition #1 (hda1) and use the free space.
Note: Remember that IDE1 master, partition #1 (hda1) represents the First partition on the First hard drive.
The partitioner will ask you how much space you wish to distribute to Linux partition, just enter the desired amount of space (I recommend around 5-6 GB). Continue with the installation.
3. After the installation is over, reboot the machine and you will be able to select from Windows or Ubuntu at boot time.