1. Are you a "code" reader for these type programs and would you be able to ascertain what they need?
2. I doubt seriously the problem is with the Codecs' themselves but rather what you're trying to use them with XP, and I seriously wonder about whether your reported error message is an actual error message.
a. "Err Msg: A Decompressor Was Downloaded for This File, But It Didn't Work (Q231325)."
b. "Windows Media Player for Windows XP Supported Codecs (Q291948)."
c. "Windows Media Services 4.1 Firewall Information."