IRiver H340 new battery won't hold a charge!!

Sounds like the battery is dead. Rechargeables only last so long. I'd copy all the content off it, before the battery dies totally, which could make it not work even connected to your computer. Looks like you can get a replacement battery: Iriver h340 Google Search
And here's a video on replacing the battery: How to Replace the iRiver H340 Battery

H340 should show as a removable disk drive. Ensure it is formatted as Fat32, run chkdsk, or scandisk. Does the H340 boot into play mode? you did not say. I replaced my battery with no problems... so if it boots Ok it is a non-related fault.

Hi, I had the same problem with my H340. I bought a battery for $16 on eBay and swapped them out. The unit would say "Charging" but would never "Complete". When disconnected from the AC, it would not power up at all. I opened it up again and noticed that the old battery connections had the red wire on the left, the battery had the red wire on the right. I took the black and red wires out of the quick-connect jack and swapped them so that the red wire would no go into the player on the left. Works like a charm now.

They may need to be on the other way.

I use iReverter

The H300 series (H320, H340) does not support movies.

The reset button will not delete any file or function, just press that.
When you connect your H340 to PC, you may right click the H340 drive icon, and select 'property' -> clean up drive

Sounds like you need to Replace the battery

Visit http://xushi.co.uk/index.php?title=revive_your_iriver_h320_h340_with_a_new_&more=1&c=1&tb=1&pb=1 to see how its done. Buy battery from link to ebay

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.