Native IIS 6 compression could be good ?

Many places with help to set it up.
http://www.it-hq.org/modules/AMS/article.php?storyid=122&page=2
http://www.wwwcoder.com/main/parentid/170/site/3669/68/default.aspx

Compression checker at Port80Software (to test your site):
http://www.port80software.com/

I ultimately used the IIS Resource kit tool to enter the "php" extension , I could not get the right formatting by editing the metabase.xml file directly.

Important: The set of headers returned by compressed IIS data does not seems to work with ColdFusion cfhttp (or cfschedule). Decided to stop using it, could be the sign of a larger problem (too risky).