Intro:

Recently I installed a new ROM to my phone and discovered all my media files (Music I have on my SD card, and any ring tones and alerts on the system that came with the ROM) were showing duplicates and sometimes more then two. At first I figured this was an issue with the ROM and ignored it. After installing a different ROM I discovered the same problem.

To Fix This:

1. Open Settings > Applications
2.  Select the All tab.
3. Scroll to find “Media Storage” and select it.
4.  Select Clear Data and confirm you would like to do this. (Note: Media will appear to be gone from phone if you don’t follow the next step.)
5. Restart phone.

6. Done!

Note:
- Menu names may vary between Android ROMs.
- Also, I have not experienced this with stock ROMs but I imagine it could happen.