***DISCLAIMER***
Editing the wrong files in this method can ruin your phone, proceed at your own risk! I will not be held responsible for any damages to your equipment. This guide is written towards somewhat Saavy computer people. If you do not understand what a filesystem is, please look for another guide.
***END DISCLAIMER***

Operating System: Windows Vista 64 Home Premium
Software QPST Verison 2.7 Build 215. Google it.

1st and foremost download install the drivers from the samsung website:
http://downloadcenter.samsung.com/content/SW/200708/20070813082717640_Samsung_USB_Driver_Installer.exe

2nd DL the version of QPST mentioned above, newer versions may work, but this is what I've been using since my U470 Juke.

Next go into Menu > Settings > USB mode. Set it to "Ask On Plug"

Connect Phone using a USB cable, I used my USB cable from my Juke which also works on the chocolate, glyde, and Trance XD. Select Modem Mode on the Phone. The other mode is for Memorycard access/ music access

Open QPST Configuration, click add port. your phone should be on Com 3 + 4. Add both ports. (you will only have to do this once)

Click start client menu, EFS Explorer. On the following screen select your phone, you'll see your # there so you will know its yours.

Go into the brew directory, by clicking the + sign. Then go to Mod folder then MR Folder.

Copy the mrinfo.db to your computer. Then Copy it again to another safe spot. This is your Go-Back Safety file.

Create your custom MP3 ring tone, I use Audacity. Keep it under a minute, I've used Ringtones 892KB large and 38 seconds. My Ringtone is called Mountain Dew.mp3

Open mrinfo.db (NOT the second one we backed up for safety purposes) with notepad or wordpad preferably. Between "CODE" and "END CODE" enter this line of text at the bottom EXACTLY as show:

------------------CODE-----------------------------
/ff/brew/mod/mr/Mountain Dew.mp3|0|8
--------------END---CODE--------------------------

Save and exit
(Note: Replace Mountain Dew.mp3 with the filename of your Ringtone)

Copy Both files to the mr folder that we copied mrinfo.db out of

Click the reset phone button, disconnect your USB cable, and enjoy your new Mountain Dew Ringtone!

Credit to vmusrh8ingnowap for this.