My Mp3 fell on the ground and the hold button is on still

Replacement batteries are available on Amazon. Turn the A829 over and remove the one recessed screw at the top centre of the back case. You will then be able to slide this part off. Careful not to lose the shield that may fall off underneath this cover.
You will now find two screws underneath holding the rest of the back cover on and also two at bottom. A set of philips watchmaker's screwdrivers plus tweezers will be helpful. Put screws in safe place.
Fully remove the back and you will find the battery which has a small connector on the lead held in place by a strip of adhesive tape. Remove connector and battery and replace with the new battery. Put tape back on the connector and then replace back of MP3 player in the reverse order that you took it off. The shield that fell off on mine fits in top centre of device - mine fell off and I had to work out where it came from!
Hopefully these directions will help you

Hold the power button for 10 seconds. this should cause reset. if it does not hold it again for 15 seconds this should cause it to power into repair mode where you will then need to plug it into your computer and update the firmware with the included software. hope this helps!

1. Power off the device (Press and hold the Sleep/Wake button for a few seconds until the red slider appears, then slide the slider. Wait for the the iPod touch to turn off.
2. Press and hold the Home button while reconnecting the USB cable to iPod. When you reconnect the USB to iPod, the device should then power on. 
   
3. Continue holding the Home button while iPod starts up. While starting up, you will see the Apple logo.
4. When you see "Connect to iTunes" on the screen, you can release the Home button and iTunes will display the recovery mode message:
5. Restore and it'll download ~240mb firmware and you're done

Warning: you will lose all your data 

Ok just fixed mine by pushing pin into reset hole. Hold play button turn zen v back on format player. yes you will lose your data but its better than buying a new mp3 player. download zen firmware update plug player in and update. This problem is caused by a corrupted file so the only way to fix it is full formate.

Fell on the ground? the hard disk inside the mp3 player may have been damaged when you dropped it in which case the mp3 player is shot.

Make sure the hold switch if off. Reset the player. Try a different USB port on same computer. Try a different computer with the same OS (to prevent formatting-related errors)
Here's some general info about the problem: 1.      1.       “My Mp3 player won’t turn on” or “My Mp3 player won’t hold a charge.” (POWER SUPPLY ISSUE)
The tricky part about these issues is that there are several possible causes – it could be software or it could be hardware.  Before you try anything else, make sure the mp3 player’s “hold” or “lock” switch is not engaged.  See your user’s manual for location of switch/ instructions (available from manufacturer’s website).  If the hold is engaged, the mp3 player will not charge, and it will not turn on.  Then, make sure the player is plugged into a compatible computer with a USB 2.0 port.  Many laptops and older desktops lack sufficient power resources to properly power/charge/utilize an mp3 player.  Next, try resetting your mp3 player.  If that still fails, try your device’s “recovery” button.  There is a specific button that triggers the recovery mode – volume + for most players, REC button for others, play for others, and skip forward for still others.  The general formula goes something like this, although you may have to substitute another button for “volume +”: disconnect the player from the computer, turn it off even if you have to reset the player to turn it off (if it is dead, this won’t be a problem), hold in the volume + button, and reconnect the player to the computer while holding the volume + button in. Keep holding the volume + button for an additional 5-50 seconds. Windows should eventually go into recovery mode and revive the player (even if it is completely dead) - it will pop up a window that says Found New Hardware Wizard.
Make sure that your mp3 player is not designed for a country other than your own – this information can be obtained from the manufacturer in most cases.  European and some Asian current systems are different than in the U.S., Canada, and Mexico.  If you plug a United States mp3 player into a European wall outlet, you will fry the player.  If you plug a German mp3 player into a US outlet, it will have insufficient power to power the player.  There are transformers available that can correct for this issue.
If you have lost the original charger for your mp3 player, try to obtain the original charger.  If the original is no longer available, check your product specs to get EXACTLY the correct voltage.  It may seem harmless to use a 5V charger on a 4.5V mp3 player, but in many cases you will damage the mp3 player by doing this.
Also, never unplug an mp3 player while it is transferring music/files/performing a firmware upgrade (and also, never perform these activities when your player is not at least 75% charged).  This is a sure way to kill most mp3 players.  As a safety rule, always check and use the “safely remove hardware” option if it is available on your computer – lower right hand corner (green arrow pointing to chip) in most Windows taskbars.  If it is not available, wait one full minute after your last file transfer to unplug the mp3 player – even if your mp3 player says “OK to disconnect.”
If your mp3 player uses AA, AAA, or any type of user-removable battery, you must take extra steps to prevent equipment damage when replacing batteries (most product manufacturers do not know this tip).  Before removing the batteries, power the player off and let it sit for one minute or longer.  Run your hand along the side of your computer tower to dissipate static electricity (or use any other method available to dissipate static electricity).  Use only and exactly the replacement battery recommended by the manufacturer.  Carefully remove the old battery.  Hold and gently squeeze the new battery for a few seconds to dissipate static.  Hold the mp3 player case in one hand, and carefully insert the new battery.  One single static spark, and your mp3 player could be history.  Also, check your product documentation beforehand to see if removing the battery will result in your song’s being erased/data being lost.  Many, if not most, mp3 players do not have replaceable batteries – the manufacturers do not have them, and popping open your mp3 player more often than not causes damage to additional components.
If the solutions above do not work, and you have gone through troubleshooting with the manufacturer, you may have hardware damage and the player will need to be replaced. -Tha Mp3 Doctor

Power & Hold switch
Slide and hold in the opposite direction
of the arrow for power on/off.
Slide in the direction of the arrow to
lock the button functions.

If that fails,
Try this: disconnect the player from the computer, turn it off, hold in the volume + button, and reconnect the player to the computer while holding the volume + button in. Keep holding the volume + button for an additional 5-50 seconds. Windows should eventually go into recovery mode and revive the player- it will pop up a window that says Found New Hardware Wizard.

Make sure the hold switch if off. Reset the player. Try a different USB port on same computer. Try a different computer with the same OS (to prevent formatting-related errors)  Here's some general info about the problem:  “My Mp3 player won’t turn on” or “My Mp3 player won’t hold a charge.” (POWER SUPPLY ISSUE) The tricky part about these issues is that there are several possible causes – it could be software or it could be hardware.  Before you try anything else, make sure the mp3 player’s “hold” or “lock” switch is not engaged.  See your user’s manual for location of switch/ instructions (available from manufacturer’s website).  If the hold is engaged, the mp3 player will not charge, and it will not turn on.  Then, make sure the player is plugged into a compatible computer with a USB 2.0 port.  Manylaptops and older desktops lack sufficient power resources to properly power/charge/utilize an mp3 player.  Next, try resetting your mp3 player.  If that still fails, try your device’s “recovery” button. There is a specific button that triggers the recovery mode – volume + for most players, REC button for others, play for others, and skip forward for still others.  The general formula goes something like this, although you may have to substitute another button for “volume +”: disconnect the player from the computer, turn it off even if you have to reset the player to turn it off (if it is dead, this won’t be a problem), hold in the volume + button, and reconnect the player to the computer while holding the volume + button in. Keep holding the volume + button for an additional 5-50 seconds. Windows should eventually go into recovery mode and revive the player (even if it is completely dead) - it will pop up a window that says Found New Hardware Wizard. Make sure that your mp3 player is not designed for a country other than your own – this information can be obtained from the manufacturer in most cases.  European and some Asian current systems are different than in the U.S., Canada, and Mexico.  If you plug a United States mp3 player into a European wall outlet, you will fry the player.  If you plug a German mp3 player into a US outlet, it will have insufficient power to power the player.  There are transformers available that can correct for this issue. If you have lost the original charger for your mp3 player, try to obtain the original charger.  If the original is no longer available, check your product specs to get EXACTLY the correct voltage.  It may seem harmless to use a 5V charger on a 4.5V mp3 player, but in many cases you will damage the mp3 player by doing this. Also, never unplug an mp3 player while it is transferring music/files/performing a firmware upgrade (and also, never perform these activities when your player is not at least 75% charged).  This is a sure way to kill most mp3 players.  As a safety rule, always check and use the “safely remove hardware” option if it is available on your computer – lower right hand corner (green arrow pointing to chip) in most Windows taskbars.  If it is not available, wait one full minute after your last file transfer to unplug the mp3 player – even if your mp3 player says “OK to disconnect.” If your mp3 player uses AA, AAA, or any type of user-removable battery, you must take extra steps to prevent equipment damage when replacing batteries (most product manufacturers do not know this tip).  Before removing the batteries, power the player off and let it sit for one minute or longer.  Run your hand along the side of your computer tower to dissipate static electricity (or use any other method available to dissipate static electricity).  Use only and exactly the replacement battery recommended by the manufacturer.  Carefully remove the old battery.  Hold and gently squeeze the new battery for a few seconds to dissipate static.  Hold the mp3 player case in one hand, and carefully insert the new battery.  One single static spark, and your mp3 player could be history.  Also, check your product documentation beforehand to see if removing the battery will result in your song’s being erased/data being lost.  Many, if not most, mp3 players do not have replaceable batteries – the manufacturers do not have them, and popping open your mp3 player more often than not causes damage to additional components. If the solutions above do not work, and you have gone through troubleshooting with the manufacturer, you may have hardware damage and the player will need to be replaced. -Tha Mp3 Doctor

ALL DATA WILL BE LOST WITH THIS PROCEDURE!! You can try a ROM recovery. - TURN OFF UNIT - Place hold switch so orange shows - Hold down the REC button with the red dot on the side of the player. - Whilst holding the REC button, press the power button as if to turn on the unit - Let go of the REC button You should see the recovery console. YOU WILL LOSE ALL DATA!! However you will also have a working player. Hope this helps.

same thing happened to me and i charged and it said to connect it to ur computer and it might work