itunes doesn't update on ipod

So you're trying to update the iPod or iTunes?

- iTunes on the iPod goes with the iOS version of the iPod. You can't update iTunes on the iPod by itself

- Since you say yo have iOS 4.2. That suggests that you have a 2G iPod. those can only go to iOS 4.2.1

Identifying iPod models

iPod touch (3rd generation)

iPod touch (3rd generation) features a 3.5-inch (diagonal) widescreen multi-touch display and 32 GB or 64 GB flash drive. You can browse the web with Safari and watch YouTube videos with Wi-Fi. You can also search, preview, and buy songs from the iTunes Wi-Fi Music Store on iPod touch.

The iPod touch (3rd generation) can be distinguished from iPod touch (2nd generation) by looking at the back of the device. In the text below the engraving, look for the model number. iPod touch (2nd generation) is model A1288, and iPod touch (3rd generation) is model A1318.

If yo need more help pleas tell us what you are trying to accomplish.