|How to create custom ringtones for your iPhone|
Follow these steps you can create ringtones for your iPhone for free.
1. Check your iTunes setting by clicking menu iTunes --> Preferences --> General --> Importing setting. Make sure the "Import Using" is set to "AAC Encoder".
2. Select the song in iTunes, control + click (or right click) the song and select "Get Info". Select "Option" tab, then input the "Start time" and "Stop time", and check both checkboxes. "Start time" & "Stop time" will be start time and end time of the ringtone you want to create. The length of the ringtone should be within 30 seconds.
3. Close "Get Info" window, select the song and select "Convert Selection to AAC." from the "Advanced" menu. A new trimmed copy of song will be created in iTunes.
4. Drag the new song to desktop and delete the one in iTunes.
5. Rename the song in desktop from .m4a to .m4r. After that, drag the song back to iTunes library. You should find the song in Ringtons section.
6. Now you can sync your iPhone and the new rigntone will be available in your iPhone.
(I tested these steps using iTunes 8 on Mac OS X leopard, and my iPhone is 3GS with OS 3.0. The steps using iTunes on Windows should be similar.)