I have a 3rd gen 15gb iPod which I either want to sell and upgrade or I can by a bigger hard drive along with a new battery for this unit and stay cheap and continue to jam out with this one. I just ran across an issue recently where battery would die after half life or 1 1/2 hours into play. It just wasn't holding the charge. I decided to crack it open and move some things around... now, guess what? Battery holds full charge for hours again... weird! Anyways. I saw someone selling a 4th gen ipod battery and was wondering if I can drop that bad boy into the 3rd gen unit. Will it do any harm? Any1 have any feedback on this or have u ever tried it?