How to execute SSI files and Tags

Hi Forum Members,

i am facing some problem with SSI files and tags to execute in my web site. below is the tag syntax.

Please let me know how to execute this scripts in IIS 7.

According to the browser agent i have to show the txt file content, means (Mobile & PC etc.)

<!--#if expr="$mode!=/Myphone/" -->
<!--#include virtual="/ssiFiles/Myheader.txt"--><!--#endif --><!--#if expr="$mode=/Myphone/" -->
<!--#include virtual="/ssiFiles/Myheader_mobile.txt"--><!--#endif -->

Thanks,

Ateeq Pasha