LinuxBSDos.com posted a quick tutorial about dual-booting Ubuntu 12.04 and Windows 7

First things first. Download a copy of Ubuntu 12.04 installation image from here. Depending on your platform, you may download the 32- or 64-bit installation image. Images used for this tutorial were taken from test installations using a 32-bit installation image in both a virtual environment using VirtualBox, and on real hardware. In either case, I did not encounter any errors that others have reported, so I am certain that if you follow this guide, you should have a computer with both Windows 7 and Ubuntu 12.04 installed in a dual-boot configuration.

So that anytime you reboot the computer, you should see Windows 7′s boot menu with two entires listed – Windows 7 and Ubuntu 12.04 (LTS). Then you may choose to boot into Windows 7 or Ubuntu 12.04.

  How to dual-boot Ubuntu 12.04 and Windows 7