1. Open iTunes, in the Library (of the PC not iPhone) locate the song you want to use as a ringtone (even if it's a full song).
2. Right mouse click the song and choose Get Info. Choose Options tab and place a check mark for Start Time and Finish Time.
3. Pick the 30-40 seconds of the song you want use as the ringtone and use the minute settings in the Start/Finish Time to set start and finish of the song. For example, the song I like is Good Girls Gone Bad by Cobra Starship. I want the first chorus of the song to be my ringtone. It begins at 00:44 and ends at 01:16. So, in the Options tab with Start and End Time check marks set I would set the Start Time to 00:44:00 and End Time to 01:16:00.
4. Click OK. This will create a copy of the song but only with the specified play time.
5. Right click the small piece you just created and click Create AAC version.
6. Right click and delete the file you just created, but choose Keep Files at the prompt. This will keep the file in iTunes folder but delete it from the application so you don't have duplicates when you sync your iPhone.
7. Go Start>My Documents>My Music>iTunes>iTunes Music, here locate the folder with either the song name you chose or the Artist name. Usually the folder is created based on the Artist's name.
8. Open the folder, if there is another one open it as well. Here you will find your song file with the extension .m4a
9. Simply right-click the file and choose Rename. Change only the extension from .m4a to .m4r and press Enter. (Optional: You can change the name of the file to your preference)
Note: Depending on your windows operating system your extension might not be visible during the rename stage of this guide because windows hides common extensions from users. In this case do the following. Open Control Panel, open Folder Options, select View tab, locate "Hide extensions for known file types" option and remove the check mark, click OK. Now the extensions are visible.
10. Open the file for Playback in iTunes by double-clicking the file. The file is automatically added to your computers Ringtones section.
11. Now, right-click Ringtones in your iPhone section and choose Sync. Done.
Congratulations you have the knowledge to upload as many ringtones to your iPhone as you like at no cost at all. Post your comments and experiences following this guide. Enjoy.