MP3 EDITING USING AUDACITY (pls googlesearch)
OK guys here is a step-by-step guide using AUDACITY (freeware) on how to cut your own MP3 to use as ringtone

1. Download AUDACITY V. 1.2.0 form this site
2. Also download LAME dll coz you need it to save your files to MP3
3. Install and Run Audacity in your PC
4. Clik File->Preferences, it will bring you to File Formats Tab
5. Click Find Library Button at lower right corner and a window will pop up, click YES
6. It will ask you to locate the LAME dll that you downloaded, find it and click OPEN
4. Now you are ready to open the MP3 song you want to edit by going to File->Open, select song
5. Play the song and determine which part of the track you want to keep
6. Bring your pointer arrow to the part of that track you want and
7. Wait till the pointer turn to a Cursor and Click, a line will appear
8 You can drag this line from left to right to create your selection (edit: pointer change to a hand)
9. Play it and if you are satisfied with it, click the button that look like "wave " near Paste
10 This "wave button" is the "TRIM OUTSIDE SELECTION", you know what it does
11. Save your work by clicking "Export as MP3", and you are done

*tutorial courtesy of friedbrains from hofo