Q: An unkown error (-1) ?

Error 1 or -1

This may indicate a hardware issue with your device. Follow Troubleshooting security software issues, and restore your device on a different known-good computer. If the errors persist on another computer, the device may need service.

The "device may need service" means a hardware problem. In that case make an appointment at the Genius Bar of an Apple store.

Apple Retail Store - Genius Bar

For updating:

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. With OSX 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. For a Mac, that requires a Mac with OSX 10.6.8 or later

Identifying iPod models