I've just finished installing Ubuntu and Windows for dual boot on separate partitions. I installed Windows first because it's pickier about partition style (MBR) and that went fine. I shrank the disk and left a bunch of free space for Ubuntu.
I then installed Ubuntu 12.04 Desktop (in low graphics mode), but after finishing the install and getting to the prompt to restart the computer, it boots straight into windows without asking which operating system to load.
I suspect that the boot loader isn't being installed properly but I do not know how to verify this.