No sound when using Movie Maker

I have a set of Creative 5.1 Surround Sound speakers connected to my computer
and I am using a composite connection from my VCR to my WinTV-PVR 150 to take
some old movies and put them on my Media Center PC. But I don't know what
audio input source to use since my speakers take up the line in, line out,
and microphone ports on my sound card. Can someone please solve my dilemma?