Download the QuickTime 7 software here:
After installing, launch the QT7 Player and choose QuickTime Player 7 > Registration from the menu bar. Enter your name, organization (if there is one), and serial number supplied in your email confirmation of purchase. Press tab between the fields, and Enter after the serial number. The logo at the left should change to say Pro. You may need to close and reopen the registration field to confirm the change.