Re: Wall chargers. Older Wall chargers use the Firewire voltage (something like 9-18VDC)charge port that was discontinued on 4th gen and higher Nanos . Even though none of the Nanos use Firewire, generations 1 thru 3 can still be charged this way. All chargers for the 4th gen, wall, car or PC USB use the same voltage of 5VDC, hence they make no difference on this model of Nano.

Very easy, provided the only problem is with the hard drive. Check that your compact flash is formated in "Fat32" (You will need a USB compact flash reader plugged into your PC to see this) Check the pin orientation and install. Perform a "Restore".

IF YOUR NANO IS UNDER WARRANTY CONTACT APPLE. If the failure is cause by water intrusion the best course may be to sell it on eBay AS-IS. If none of above apply, you may consider a screen replacement. Several generations of Nanos, all seem to suffer from LCD failure, "White screen of death" This can sometimes be fixed by an LCD screen replacement. Fortunately, on the 4th gen Nano, this is a relatively simple, but should only be attempted by an experienced technician. See Fixit guide on this website Replacement screens may be purchased on eBay for ~$10.

Possible corrosion at LCD ribbon to main board connector.