Please find steps to customize ringtones.
Note: in order to be able to use this method one has to have two Motorola phones: the W510 and an older one that isn't ringtone-locked (I tried a V190 and and RAZR V3 and both worked).
First create a backup directory on your drive and call it something like "Original Motorola W510 audio directory". The name doesn't really matter as long as you can find it later if you ever need those files again. Next install the ringtones you want to have on your W510 to the old uncrippled phone.
Then follow these steps:
Step 1 - Connect the W510 to your computer via USB or Bluetooth
Step 2 - Fire up P2K (latest version)
Step 3 - In the right pane navigate to P2k:/c/mobile/audio/ on the W510; in the left pane navigate to the backup directory you just created on your hard drive. It will be empty.
Step 4 - Select all the files in P2k:/c/mobile/audio/, right-click and select "copy", the files will be automatically pasted in your backup directory.
Step 5 - Delete all the files in P2k:/c/mobile/audio/. Once this is done the "audio" directory will have vanished so it's possible that P2K will crash, this is not a problem.
Step 6 - Create a new directory on your disk, name doesn't matter. Unplug the W510 from the computer and reboot it (the phone), then close P2K (if it hasn't crashed already) and plug the older Motorola phone into the computer, wait for the computer to recognize the new phone, then restart P2K. On the right pane navigate to the old phone's audio directory (same location as on the W510), on the left go to the new directory you have just created.
Step 7 - use the method described in Step 4 to copy all the files in the audio directory to your hard disk. *Do not erase any files in the old phone's audio directory*
Shut P2K down and unplug the old phone from the computer. Plug in
the W510 and wait for the computer to recognize it. Once this is done fire up P2K once more.
Step 8 - Remember that the audio directory on the W510 is gone, so you can't navigate directly to it, you need to create it first. In the right pane go to /c/mobile/ and select "New Folder" from the menu at the bottom of the pane. Name the new folder "audio" and navigate to it.
Step 8 - In the left pane navigate to the new directory on your hard drive that contains the audio files from the old phone.
Step 9 - Copy all those audio files to the new audio
folder you just created on the W510.
Step 10 - That's it, your W510 now contains every single ringtone that was on your old phone and all of them now have the "apply" option enabled so the W510 will now accept any of those sounds as a ringtone.
Unfortunately the W510 still won't accept sounds from any other source than the old phone but as long as you're able to get those those sounds (inclding custom sounds) to register as ringtones on the old phone you'll be able to transfer them to the W510 using the method described above. It's a little tedious but there ain't no such thing as a free lunch is there