Codeigniter 2 on IIS with web.config file

Have you look at the example in the CI forums?

http://codeigniter.com/forums/viewthread/91954

<?xml version="1.0" encoding="UTF-8"?><configuration>    <system.webServer>        <rewrite>            <rules>                <rule name="Rewrite to index.php">                    <match url="index.php|robots.txt|images|test.php" />                    <action type="None" />                </rule>                <rule name="Rewrite CI Index">                    <match url=".*" />                    <conditions>                        <add input="{REQUEST_FILENAME}" pattern="css|js|jpg|jpeg|png|gif|ico|htm|html" negate="true" />                    </conditions>                    <action type="Rewrite" url="index.php/{R:0}" />                </rule>            </rules>        </rewrite>    </system.webServer></configuration>  

i have placed the following web.config code in the root and it worked perfectly.

<?xml version="1.0" encoding="UTF-8"?>    <configuration>        <system.webServer>            <rewrite>                <rules>                    <rule name="Imported Rule 1" stopProcessing="true">                        <match url="^(.*)$" ignoreCase="false" />                        <conditions logicalGrouping="MatchAll">                            <add input="{URL}" pattern="^system.*" ignoreCase="false" />                        </conditions>                        <action type="Rewrite" url="/index.php?{R:1}" />                    </rule>                    <rule name="Imported Rule 2" stopProcessing="true">                        <match url="^(.*)$" ignoreCase="false" />                        <conditions logicalGrouping="MatchAll">                            <add input="{REQUEST_FILENAME}" matchType="IsFile" ignoreCase="false" negate="true" />                            <add input="{REQUEST_FILENAME}" matchType="IsDirectory" ignoreCase="false" negate="true" />                            <add input="{R:1}" pattern="^(index\.php|images|robots\.txt|css)" ignoreCase="false" negate="true" />                        </conditions>                        <action type="Rewrite" url="index.php?{R:1}" />                    </rule>                </rules>            </rewrite>        </system.webServer>    </configuration>

It turns out I didn't have Rewrite installed. This did the trick:

http://www.iis.net/downloads/microsoft/url-rewrite

I'm not sure if codeigniter's error page may have masked the error somewhat, because I couldn't determine that it wasn't installed from the browser's error screen. Also Event Viewer, IIS logs, and PHP logs all were not helpful for this situation.