When I installed Ubuntu 12.10 I decided to install it on a separate hard drive from my Windows 7 install. Windows is installed on a 1.5TB hdd and I had an extra 500GB hdd that I intended to use for Ubuntu. I installed the hard drive in my PC and booted up the 12.10 installer. When the “installation type” window came up I chose “Something Else” and then “continue”. This popped up a partition editor and I was able to see both drives in the list. Because they were both different sizes, it was easy to determine which was which. In my case the windows drive was called /dev/sda while the new drive was called /dev/sdb. I had used the drive before so there was a bunch of partitions that I needed to erase. To do this I just selected the partition I wanted to erase and clicked “Delete”. Once they were all gone I was left with one item under /dev/sdb called “free space”. I selected this and clicked “add” to create a new partition. Under “Mount Point” I picked “/boot”, I made the size 500MB, left the rest at default and clicked “OK”. I created another partition for root choosing “/” under Mount Point, Logical for the type, and a size of 50,000MB. For the next partition I selected “swap area” under “use as”, making it 4000MB, I clicked “Logical” for type, and “End” for location. Finally for the last partition I used the remainder of the drive for the home partition. I chose “/home” under Mount Point, “Beginning” for location and “Logical” for type.
To make sure I could boot into both Windows and Ubuntu, I selected /dev/sdb under “device for boot loader installation”. and then clicked “Install now”. Once the install was finished I rebooted the computer and pressed the delete key to enter the BIOS. I set the second Ubuntu hdd as my primary boot device and BAM! I was dual booting with windows.