Error when file attempts to download...

I've applied the dfp download function to a button on my audio page following the instructions from the "How to create a download center" tutorial. When ever I hit the download button the browser stops responding for a moment the dumps the following error along with a bunch of strange code. I can tell that the file is mapped correctly because I can pick out the name of the file in all of the junk code. The error is as follows:

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\yourWorkingCopy\audio.php:6) in C:\xampp\htdocs\yourWorkingCopy\WA_DigitalFilePro\HelperPHP.php on line 688

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\yourWorkingCopy\audio.php:6) in C:\xampp\htdocs\yourWorkingCopy\WA_DigitalFilePro\HelperPHP.php on line 689

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\yourWorkingCopy\audio.php:6) in C:\xampp\htdocs\yourWorkingCopy\WA_DigitalFilePro\HelperPHP.php on line 690

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\yourWorkingCopy\audio.php:6) in C:\xampp\htdocs\yourWorkingCopy\WA_DigitalFilePro\HelperPHP.php on line 691

I've attached the file also. If you could help I would greatly appreciate it.

Thanks
James