I am still getting the same error. I am now getting the following:
DownloadManager Information: 0 : Adding product 'Moodle' to the cart
DownloadManager Warning: 0 : product.SelectedInstaller == null for: PHP53ForIISExpress
DownloadManager Information: 0 : Starting install sequence
DownloadManager Information: 0 : Using cached file at C:\Users\Administrator\AppData\Local\Microsoft\Web Platform Installer\installers\Moodle\a9dd9a95e29c8f821f2005f8b8675281b1ff8f38\MoodleWindowsWpi-latest-23-20121121.zip instead of downloading from http://download.moodle.org/download.php/direct/windows_wpi/MoodleWindowsWpi-latest-23-20121121.zip
DownloadManager Information: 0 : Testing database connection string
DownloadManager Information: 0 : Using connection string: 'server=localhost;database=moodle715;uid=root'
DownloadManager Information: 0 : Setting DeploymentBaseOptions.WebServerDirectory: C:\Program Files (x86)\IIS Express
DownloadManager Information: 0 : Setting DeploymentBaseOptions.ConfigurationDirectory: C:\Users\Administrator\Documents\IISExpress\config
DownloadManager Information: 0 : Setting DeploymentBaseOptions.WebServerDirectory: C:\Program Files (x86)\IIS Express
DownloadManager Information: 0 : Setting DeploymentBaseOptions.ConfigurationDirectory: C:\Users\Administrator\Documents\IISExpress\config
DownloadManager Information: 0 : Moodle installation log: C:\Users\Administrator\AppData\Local\Microsoft\Web Platform Installer\logs\install\2012-12-09T13.46.01\Moodle.txt