I wish I could...I can transfer MP3 files and it is part of my music on my phone..but I don't think I can turn my music into ringtones.
Look for a program called "BitPim". It's freeware.
I use it to put ringtones on my Verizon phone. You put MP3s onto a mini SD card, in a directory called "ringers" (or something like that, BitPim help file and website will tell you how). You then plug your phone in with a USB cable (I bought mine for $3 from ebay), BitPim then looks for all files on the memory card, and tells your phone where to look for them as ringers.
The only problem I've found is that if you power off the phone, it "forgets" where the ringtones are saved. So if I go on a plane, etc, I have to make sure to put the phone in Standalone mode, and not powered off. Otherwise the phone is silent when it rings with one of those "lost" ringers.
I have a ton of Disney ringers on my phone for both phone calls and texts, to the point where many people in my phone book have their own. Though some of them are too long and they just stop if the call drops to voicemail. (Though what's nice is that if you test the ringer out in the selection menu, it plays the whole thing no matter how long it is)
-MSEP
-"Yo Ho", both instrumental and with French vocals
-a 1950's/60's pre-recorded voice from Disneyland saying "Attention, please. Attention, please" (that's my text message alert)
-Opening fanfare and "procession" music from Share A Dream Come True parade (no dialog)
-The communication tunnel from pre-2007 SSE
-Four segments of RoE (Chaos, Adventure, Home, Celebration)
-The "Welcome aboard the WDW monorail system spiel" en route to the TTC
-HISTA theme
-Mansion wolf howl
-"Dead men tell no tales..." (those last two are a little freaky if they're set to my text message alert and it goes off in the middle of the night...)
I also have a couple Muppets ringers, including their "Stars & Stripes Forever" YouTube video and Animal going "Duh DA DA DA!" from the Swedish Chef/Beaker YouTube video.
-Rob