A few months ago I bought an iPod classic 4th gen from Ebay. I did a factory reset on it (just to be safe) and it worked great. I used it a few times then set it aside for a while (while trying to find a car cable for it). The AC in my house died and it got pretty hot for 2 days while I waited for the repair guy. I tried to use it the other day and it was dead. Figuring the battery was dead, I put it on a wall charger all night and it still didn't turn on. I get absolutely nothing. I can't do any sort of reset since it won't turn on. And it won't register on my Mac Book either - like I never plugged it in. I tried Apple's help site and all they have to say is charge it and reset it, pay to have Apple fix it, or buy a new one. I have a touch and I hate it A LOT. Help, please.
If you are good with small tools and cables you can try dis-assembling the iPod and replace the battery (which you can probably purchase for $20.) See iFixit: http://www.ifixit.com/Guide/Installing-iPod-4th-Generation-or-Photo-Battery/393/1
You can also take it to the Apple Store and have them try charging it with a Firewire cable (I've seen those occasionally revive a dead 4th Gen iPod.)
Unfortunately that iPod is approx. 7 years old, so it may not have been long for this world...