i have the i pod touch 2g how do i upgrade to the 4.2.1

To update

The Settings>General>Software Update comes with iOS 5 and later.

Connect the iPod to your computer and update via iTunes as far as your iPod model allows

iOS: How to update your iPhone, iPad, or iPod touch

A 1G iPod can go to iOS 2.2 via iTunes and iOS 3.1.3 via

Purchasing iOS 3.1 Software Update for iPod touch (1st generation)

https://buy.itunes.apple.com/WebObjects/MZFinance.woa/wa/touchLegacyLandingPage

A 2G to 4.2.1. Requires iTunes version 10.X. If a Mac it requires OSX 10.5.8 or later.

Identifying iPod models

If your iPod does not have volume buttons on the upper left edge it is a 1G

Update it from iTunes on a computer as described at the bottom of this article; devices running an iOS version prior to 5.0 can't be updated straight from the device.

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