There is an easier way to do it for free...Have fun
Go into your iTunes preferences, and make sure you are using the AAC encoder. You can double-check this by going to “Advanced”, then “Importing”. Now, browse to the song you want to use to create your ringtone. Right click on the file, and choose “Get Info”, then “Options”. Under the Options tab, select te start time and stop time, to create a 30 second clip. Once your 30 second clip is selected, right-click the song and choose “Convert Selection to AAC”.
Once the conversion is completed, you will get a 30 second song of the same name. At this point, you can edit the original file back to its normal length. Now, browse to your iTunes music folder. You should find the new clip in the same folder the full-length song is in. Notice that the clip has an extension of .m4a. Simply rename the extension to .m4r, then select it. It will automatically be added as a ringtone in your iTunes library.