There's two ways you can do it.
1) From the Tron 2.0 main menu, go to Options > Sound > Sound effects volume and turn it all the way down. This silences the music in the cutscenes. Then use a program to record the dialogue.
2) Visit my files page
and download Winrez LT. Install it, and use it to open the Sound.rez file in your Tron 2.0 folder. All the voice files are contained in it. You can extract files with Winrez as well.