Hi guys
Might be dragging up an old thread but I this was one of (if not the) the very first google finds for my question so it might come up in the future for others.
I may be repeating other people, but i'm just gonna add the steps that I took in order to accomplish this.
Hope it's useful.
First off, I'm running the 2.2 firmware on my iPhone 3g which has been jailbroken using cydia. (And I'm running Windows)
Then i installed
iPhonebrowser
You then start iPhone browser and plug in your iPhone, and move to the System > Library > Audio > UISounds folder
By now you should know which sms ringtone you like the least, and the number corresponding with it. (For me, it was electronic, which is number 6)
Find sms-recieved#.caf (where # is the number of your chosen ringtone) and right click, backup file, for just in case you ever want it back.
Next, you replace this file with your new ringtone. If you've already got your file, ignore this bit, if you haven't, read on my loveleys.
Download and install switch audio convertor (google it, it's free).
Then drag and drop your sound clip into this program, change the output file to aiff and hit convert (as long as you know where the file will end up, I've ticked output same as source file so it ends up right next to my original)
Then in windows explorer change the extension of the new .aiff file to caf (if the file isn't called example.aiff look around in folder options for the ability to see file extension names) and also the name of the file to sms-recieved#.
Back into iPhone browser, right click sms-recieved#.caf and choose replace file, then choose your new ringtone.
After all is done and dusted and the iPhone is unplugged you must RESTART the iPhone in order for the sound to play. This was an issue I first had.
Sorry it was a bit long winded, just wanted to fully clarify the actions you need to go through.
However, if you're having problems changing ringtones and following instructions, should you really be jailbreaking your iPhone in the the first place? And playing with settings and files?
Just want to thank dsgalit for his original post.
It helped me on my way
Cheers dude
(Hope I haven't come off as a complete cock in this post)