If your new to Linux, your first encounter w/ it's partition tools can be scary. So I'm going to describe a way to fix your problems w/ a 3rd party partitioning application. So let's get started. You need to download Bootit NG and either burn it to a CD, put it on a floppy or SD card if your bios allows you to boot from one.
Now reboot into Bootit (making sure the device/CD/floppy is first in order of bios, if it fails to boot on first try).
1. When Bootit menu screen comes up, choose "Cancel" (you don't need to install this to do what you need done).
2. It'll direct you to it's Desktop and hopefully your mouse will be enabled to make it easier. You'll see an icon to the left that says "Partition Work" (if not, use tab key to cycle thru choices). Click on that one!
3. All your drives and partitions will show up (make note of where your two Ubuntu installs are beforehand). Depending on which one you want to keep (ref the size) you can simply delete the partition you don't want.
4. After deleting it, you'll have an empty space there. You can then change the size of the partition either before or after the space left by the delete if you click "Resize" while that partition is hi-lighted.
5. You can also slide and reduce the size of partitions easily with this tool.
So lets say you wanted to keep that first install. Even though it's small, you can resize it to take the empty space left by the deleting of your second install (if you installed them side by side). You're Done!
Now this isn't going to fix your Boot Loader. But only one install in it, is going to work now. You can fix that, after you learn more about the linux tools. This will at least get you into a larger partition and delete the one you don't want. Once you reboot after removing the disc/floppy/SD card (since you haven't fooled w/ the MBR), you will have the same boot list. Then once booted back into Ubuntu you should be able find the boot editor, to delete the one you don't have anymore. I use Gentoo and Sabayon Linux, so this is all the futher I can instruct you.
(ok just notice a mod has answered since I was a little slow posting after logging in)
You can either choose to wait for an answer from someone who knows Ubuntu from the inside out or give this a try. I have used Linux and Bootit NG for well over 12yrs and it is a remarkable tool that can restore deleted or lost partitions, format and reorder both drives and partitions along with more than I could ever explain here. Hopefully it can help you out!