I use K-lite, free, even though I paid for InterVideo. IV won't work on my computer for some reason, I think it's a conflict somewhere, if you want to try I'd be willing to let ya use the code. Iv and K-lite both work perfectly from what I've found, when I can get IV working anyways.

Basically what I bought, IV is:
DVD XPack Features
* NEW! NVIDIA PureVideo™ Technology Support
* NEW! Compatible with MCE Emerald DVD Playback
* Enables playback of DVDs in Windows Media Player under Windows XP
* Fully integrated with Windows Media Center or Media Player 9.0 or higher
* Seamlessly works with NVIDIA® GeForce™ 6 Series graphics processing units
* "Install and enjoy" simplicity
* WMV-HD Hardware Acceleration provides high definition video
* Dolby Digital (AC-3) audio decoding
* Down-mixes 5.1 soundtracks to 2-channels for optimum sound
* Fully compatible with Microsoft DirectShow
* Support for DirectX Video Acceleration to minimize CPU load
DVD XPack System Requirements
* PC running Microsoft Windows XP
* Windows Media Player version 9 or higher or Windows Media Center
* Intel Pentium 4 1.0Ghz, Pentium M 1.0 Ghz, or AMD Athlon 1.2 Ghz or higher processor
* DVD-Rom Drive
* DirectX Video Acceleration (DXVA) compatible graphics processor supports
* DirectX 9.0 or higher * For maximum performance on NVIDIA® PureVideo™ technology support.