[ Thanks to finid
for this link. ]
“If you are looking to dual-boot both operating systems on a
computer with a single hard drive, it is recommended that you read
how to dual-boot Windows and Ubuntu 11.04. As the title suggests,
it was written for Ubuntu 11.04, but because the installation
program in Ubuntu 11.10 did not change, the steps still applies to
it.“It is taken for granted that the computer that you are going to
use already has two internal hard drives with an existing
installation of Windows 7 on the first disk and the second hard
disk ready for use. Note that you do not have to re-install Windows
7, but nothing stops you from doing it. “