Where exactly is the index.php located?
Try using the new xampp-control-3-beta.exe file in the xampp folder instead of the older 2.5* version to start Apache and MySQL and see if the log window of the CP3 has any clues.
If there is an index.php in the htdocs folder and the Apache server is running then it will show that index.php not a folder listing.
Type in your browser http://localhost
- does that work and give you the XAMPP Welcome page?
Have you any error messages in the xampp\apache\logs\error.log file?
Any clues in the access.log file in the same folder?