CAPTCHA on chapter 11 of "Headfirst PHP & MYSQL"

Hello,

I copied the final Captcha program and all of its associated files from headfirstlabs.com site and run it on my IIS 7.0 server that has excellent PHP functionalities, I got the following errors:
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Server Error in Application "ELIJAH_MEKE"Internet Information Services 7.5
Error Summary
HTTP Error 500.0 - Internal Server Error
The page cannot be displayed because an internal server error has occurred. Detailed Error Information
Module FastCgiModule
Notification ExecuteRequestHandler
Handler PHP_via_FastCGI
Error Code 0x00000000
Requested URL http://localhost:80/captcha.php
Physical Path G:\LocalSites\Elijah_Mekwunye\wwwroot\captcha.php
Logon Method Anonymous
Logon User Anonymous
Most likely causes:
•IIS received the request; however, an internal error occurred during the processing of the request. The root cause of this error depends on which module handles the request and what was happening in the worker process when this error occurred.
•IIS was not able to access the web.config file for the Web site or application. This can occur if the NTFS permissions are set incorrectly.
•IIS was not able to process configuration for the Web site or application.
•The authenticated user does not have permission to use this DLL.
•The request is mapped to a managed handler but the .NET Extensibility Feature is not installed.
Things you can try:
•Ensure that the NTFS permissions for the web.config file are correct and allow access to the Web server's machine account.
•Check the event logs to see if any additional information was logged.
•Verify the permissions for the DLL.
•Install the .NET Extensibility feature if the request is mapped to a managed handler.
•Create a tracing rule to track failed requests for this HTTP status code. For more information about creating a tracing rule for failed requests, click here.
Links and More InformationThis error means that there was a problem while processing the request. The request was received by the Web server, but during processing a fatal error occurred, causing the 500 error.
View more information »

Microsoft Knowledge Base Articles:

•294807
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Kindly help if you could.