What about if my iPod doesn't have an "software update?"

That comes with iOS 5 and later.

To update if it can be updated:

iTunes 10 for Windows: Update and restore software on iPod, iPhone, or iPad

A 1G iPod can go to iOS 3.1.3

A 2G to 4.2.1. Requires iTunes version 10.X. That requires a Mac with OSX 10.5.8 or later. With 1OSX 10.4.11 you can only go to iTunes 9.X which gets you as high as iOS 4.1

A 3G to 5.1.1 Requires iTunes version 10.5 or later

A 4G to 6 Requires iTunes version 10.7 or later. That requires a Mac with OSX 10.6.8 or later

Identifying iPod models

That means you do not have iOS 5 or later installed.

Upgrading iOS

1. How to update your iPhone, iPad, or iPod Touch

2. iPhone Support

3. iPod Touch Support

4. iPad Support

a. Updating Your iOS to Version 6.0.x from iOS 5

Tap Settings > General > Software Update

If an update is available there will be an active Update button. If you are current,

then you will see a gray screen with a message saying your are up to date.

b. If you are still using iOS 4 — Updating your device to iOS 5 or later.

c. Resolving update problems

1. iOS - Unable to update or restore

2. iOS- Resolving update and restore alert messages