Hello tom34diy and welcome to
There are several threads on computer building basics HERE, so I won't go into details in this thread.
In a nutshell, if you want to eleminate the 9 Gig, you will need to start from scratch. There are programs that allow you to make an "Image file" of your existing drive and copy that to your new drive, therefore reducing some of the steps.
If you are adding this new 80 Gig to have more storage, you can add it as a slave and leave the 9 in place.
Take a look at the link above, see how the different configurations work, and then decide how you would like to go.
If you have more questions, post back and we will be more than happy to help further