Preparing your system for dynamic development for Windows Vista - Configuring IIS

I'm stuck on page 9 in the Preparing your system for dynamic development PDF file that is from Webassist. - I'm stuck on the section for "Configuring IIS for Vista"

Here are the steps
1. Open the IIS manager by going to Start > Control Panel > Administrative Tools > Internet Information Services.
2. In IIS Manager open up Handler Mappings in the IIS area.
3. Click on "Add Script Map..." in the upper right of the window.
4. In the interface that opens enter the following values .
Request path: *.php .
Executable: C:\php\php5isapi.dll .
Name: PHP



5. Click OK, the Add Script Map dialog appears and ask if you would like to enable this ISAPI extension, click yes if you want to give permission to the php module to run on IIS.


When I try to follow step 5 I get an error message saying:

"The specified module required by this habdler is not in the modules list. If you are adding a script map handler mapping, the IsapiModule ot the CgiModule must be in the modules list."



Can anyone assist me on this step or how to go arround this error message