Where can i download the original music and player app for Samsung i9000 to be used with Android 4.1.2? On the i9000, I have updated the ROM to Android 4.1.2. I would like to re-install the original music player as well as the video player.

How do I do this?
i9000 does not have an official ROM, so I'm assuming you're using a custom ROM like CM10. Stock players from Touchwiz are rarely availble, and for the most part do not work flawlessly on AOSP based ROMs.

Try Winamp and MPlayer as alternatives, they work on any ROMs so you can move freely between ROMs too.