OK guys,every one loves to have her/his own costumed ringtone that created from his/her favorite song and Apple knows that very well that's why it tends to charge us for ringtones that were created from the songs we already bought through iTunes ,thats is silly of Apple!!!. Now enough with the paying of Apple for the ringtones created through iTunes and let me display you two methods where you can create a Ringtone out of any song (including bought from iTunes). both worked fine with me ,no iphone hacking or jail breaking is needed.

The first method:

1. Open iTunes and select a song you want.
2. Listen to the song and choose the start and the end time for the section that you want to use as Ringtone.
3. right click the song and select 'Show in Windows Explorer'.
4. make a copy of this song in new folder in Windows Explorer with new file name of you choice for example 'Ringtone s'.
5. double click this song it will run into the iTunes or drag it into the Music library in iTunes.
6. Right click on this song and select 'Get Info'.
7. Here you will find various tabs go to options can put Start and stop time you chose on step 2 then hit OK
8. Then right click that song again and select 'Create AAC Version'.
9. Now you will see this song with changed time in your music library. At this time you may can delete the duplicate file you created earlier.
10. Once more,right click the song and choose 'Show in Windows Explorer'.
11. In the Windows Explorer change the extension of this song from *.m4a to *.m4r.
    
12. A warning MESSAGE will display, hit OK.now you created a ringtone.
    
13. Double click on this ringtone. iTunes will automatically show you this file under Ringtones. If you notice, the ringtone you created will have been automatically moved to /iTunes/iTunes Music/Ringtones folder.
14. Sync your iPhone to see this ringtone on your iPhone.
15. Enjoy.

I FOUND this youtube video for you to explain the above





The Second method:
This method is easier it involve the using of simple software called iPhone Ringtone Maker as following

1. download the software from here
2. Install the program then launch it
   
3. Click on Browse Computer and look for the song that you want to creat a ringtone from, then press OK
4. Now click on (Go advance), and uncheck Fade In and Fade Out ,in order to prevent the the sound of tone increasing up gradually at the start and then لradually decrease the sound at the end of the tone. Put this up to you.
5. Then search for your favorite part of the song which you want to be the tone for your iPhone. Control by the green arrow for the beginning of the tone and the red arrow to the end of the tone, note that you can only choose 30 seconds for the tone ... and you can then hear the clip by clicking Preview.
   
6. After you have selected the clip click on Create Ringtone and wait some seconds until the tone being created.
7. Then click on Send Ringtone to iTunes.
8. Rectangle will appear to you to determine the name of the tone then click on OK.
9. after that iTunes program will automatically put this file under Ringtones.
10. sync your iPhone with your PC to see this ringtone on your iPhone.
11. Enjoy
    

For MAC users her is a good guide