Resuelto.
realmente no si si es la manera correcta. Al momento me funciona!
Gracias!!!
<?xml version="1.0"?>
<configuration>
<system.webServer>
<rewrite>
<rules>
<rule name="RewriteUserFriendlyURL1" stopProcessing="true">
<match url="^(.*)$" />
<conditions>
<add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" />
</conditions>
<action type="Rewrite" url="/index.php?s={R:1}" />
</rule>
</rules>
</rewrite>
</system.webServer>
</configuration>