Many users are finding that they must manually enable ringtones in iTunes. If you are not seeing a bell beside any of the songs in your iTunes library, this is what you need to do.
Purchasing ringtones for your iPhone through iTunes is now possible. However, many people are not seeing it as an option.
First of all, be sure that you have updated to the latest iTunes software. In OS X you can update from the iTunes menu and then Check for Updates. In XP/Vista you will find the update option from the Help menu.
Next, you will need to enable the Ringtone view. From the View menu, select View Options.
From the dialog box, select the Ringtone option and click the OK button.
You will asked if you want your music library searched for potential ringtones. Select the Check Songs button.
Now in your iTunes library, you will see a bell beside the songs for that you can purchase a ringtone.
