Well, personal ringtones are stored in any folder called "ringtones" on your SD card (notification ringtones are stored in any folder called "notifications"). Note that these folders may be in other folders on your SD card.
Perhaps the best solution is to connect the SD card to your PC and use the file explorer to look for these folders on the SD card.
As for standard ringtones, these cannot be removed unless you have a rooted phone. Is your phone rooted?
