How to install a ringtone into internal memory? I am using a custom ringtone. It is a mp3 which is stored on the external SD card.

When my phone is connected via USB to my computer and the SD card is mounted, my phone uses a default ringtone on incomming calls.

How can I use a custom ringtone without SD card?
If you have root, it is possible, but not really recommended. If you do not have root, then you cannot. The file system is designed to be readonly and you can't add additional files to the system.