It seems not an easy task to find a working converter for Vista! Did a quick Google, and of course about 300 programs popped up on some suspicious sites.
But I really need to convert a few protected iTunes videos. I tested a couple of sites and detected MelodyCan converter. Their free trial is quite impressive and allows converting video and audio formats both protected and standard ones. The main requirement is the ability to play the original file in Windows Media Player (for WMV) or QuickTime Player (for M4V). Their URL is MelodyCan: Convert Any Purchased or Copied Audio and Video Files, Audio CD Ripper, YouTube Ripper Plug-in

MelodyCan is tool for converting any kind of audio and video data to commonly used formats such as MP3, AAC, WAV audio, MPEG4, DivX movie. If you need a simple, yet very efficient tool to convert (encode) or play any Multimedia file, without reading manuals or spending long hours training, then MelodyCan is all you need. Supports most video formats and also portable formats.

Download Here :

MelodyCan: Convert Any Purchased or Copied Audio and Video Files, Audio CD Ripper, YouTube Ripper Plug-in