Do this:
1. Make sure you have purchased the MP3 option from the Digistore.
2. After downloading the file from the link you received via email, go to Start > Search > All files and folders. Type in "mp3.dll" and look in the C: drive. Leave the Search window open.
3. Go to C: > Program Files > Common Files > Digidesign > DAE > Codecs > MP3, and drag the MP3Demo.dll to the trash.
4. From the Search window, drag the MP3.dll file (the one from the Paid Download folder) into the MP3 folder.
5. Launch Pro Tools, and select "Bounce to Disk." Choose MP3 as the format, and enter the serial number contained in your email. All should work fine!!