ModSecurity it is not compatible with IIS 6 as said: - http://marc.info/?l=mod-security-users&m=134878852205436 - http://marc.info/?l=mod-security-users&m=134878771004665 - http://comments.gmane.org/gmane.comp.apache.mod-security.user/10225 Installer should be fixed, here: https://github.com/SpiderLabs/ModSecurity/blob/master/iis/installer.wxs#L91-L92