Divx encoding + XP Pro SP1

[oldtecho]

I am running XP Pro SP1 +WMP9 and am trying to use the Divx codec (5.05) to encode video files. When I try and use an application like virtualdub or showshifter to encode files the Divx codec does not appear in the list of available codecs in the above applications. The Divx codec appears in the list of codecs in the XP Pro control panel and Divx encoded files play ok. I have seen postings on another website that say MS is blocking the use of 3rd party codecs in XP Pro that could violate their copyright. The other machine I have has XP Home on it and it works fine. Can anyone confirm this or do I have an install problem?