Before you proceed with that configuration, i would highly recommend that that you consider running a virtualization app rather than setting up a multi-boot configuration. The multi-boot adds additional complexity, is more difficult to manage, and doesn't allow you to run the OSs at the same time.
If the host comouter is running Windows 7, i would install Virtual Box or VMWare. Then, install Ununtu and any other OS as guest VMs. The mainadvantage here is that this is a very simple configuration. As you are done with the guest VMs, you just delete them. You can run them at the same time. This config allowa you to build a very nice virtual lab.
Vmware and VirtualBox are just two examples of apps that provide virtualization. They install on top of Windows 7. Ubuntu would run virtually within VMWare. The virtual app creates a virtual computer within Windows 7. You can run multiple VMs at the same time.