We all know you can get one big headache if you install ubuntu on the wrong internal hard drive when you have 2 or more hard drives with different os on them.
I am in the process of installing ubuntu on a spare internal hard drive and the /dev/sda or b or c or d can get very confusing.
To find the correct hard drive here is a way to locate it.
Insert the live cd and restart. Of course you have to hold down the c key when you hear the chime.
Select Try ubuntu.
After ubuntu loads up, go to System (at the top bar-you will see it. Click it.
Click on Administration. In the pop up window go to Disk Utility. Click it.
Here all of your drives are listed. You can click on each one to get detailed information about them.
It tells you the /dev/sd_ where_is the letter you are looking for.
I haven't installed ubuntu yet, but will this weekend.
I hope this might help someone like me who isn't quite familiar with ubuntu.
Good luck!