Vob playback: distorted audio

I am trying to playback .vob files as I have done on my XP laptop. This is on a new build, Vista 64-bit, Core i7, 6gb. When using Media Player Classic, the audio is just a stream of digital clicks.

When using Nero 7, there is no audio and I am told "The multimedia file you have selected requires the use of Dolby (R) Digital. Nero is pleased to offer you access to this technology with a FREE 30-day trial."

On my old laptop, they play just fine using Media Player classic. Is there something I am missing or need to install (without having to eventually pay Nero after their free trial)?

Thank you.