Stumpled across this mod_rewrite for IIS 6.0, I haven’t tried it myself yet. But if you are interested in a FREE URL Rewriter for IIS, this might be a good option?
IIRF is a small, cheap, easy to use, URL rewriting ISAPI filter that combines a good price (free!) with good features. It is reasonably fast, and reasonably powerful. You can get the source code to inspect it or modify it yourself if you desire. If you use IIS, you can download IIRF and get started right now. Or, Visit the IIRF Forums to ask a question.
Read more and download at source.