I have a fourth generation iPod and I have always been generally pleased with it. It is the last generation that had a black and white screen and I was glad to have it because the thing will go weeks to months between charges (casual use).

However a little while ago it started having problems. At first I was able to reinstall the firmware and get it running again, however that did not last long. Soon it started having sync errors in the middle of a transfer and that would destroy the entire device and I would have to reload it.

So it ended up on a shelf for a while until I came across this article on CrunchGear that described a design flaw in the iPod shell that would cause a drive to stop working. Apparently the heat produced by running a iPod for long periods of time will warp the metal shell on the under side such that it releases the pressure on the hard drive inside, which causes the drive to stop working. Therefore, to get the drive working again, all you have to do is put the pressure back onto the drive.

I finally got around to trying it for myself. The article gives better instructions but I basically took a small screw driver and pried the iPod open at its seam. The I took a business card and folded it into fourths and placed it on the middle of the drive and then just snapped the iPod case back together. It worked like a charm. I could hardly believe it. I am still using it today.

Although, this fix is kinda hit and miss; because I recommended it to a friend to try as well and he had no luck.

Here is the CrunchGear that has good pictures and better instructions.
http://www.crunchgear.com/2007/03/05/crunchgear-how-to-fix-an-ipod-that-wont-boot