Heres the link, I like the program a lot but you can judge it, its called Switch audio converter and is free. It converts different types but convert the file you want to .aiff and just rename the file to .caf it will work I've used it before to get the euro trip - mail motherf*&ker tone for my sms alert.
http://www.softpedia.com/get/Multime...s/Switch.shtml