Transfer Music Theme from TV recording to Mobile via PC

Hello!

not sure if this is the right forum (please feel free to kick it to the right one) how and ever.....

I have taped a tv show onto my Sony hard disk recorder....have it burnt onto to dvd.

I am trying to capture the music from the ending and use it as a mobile ringtone.....

How do I do this?

My tech ability is limited, though growing by reading the posts on the tech forum etc, and any help on this would be welcome.....

Ta....