Q: I can't seem to update my ipod touch on my new computer.

What happens when you try?

What model iPod do you have? You have either a 1G or 2G iPod

Identifying iPod models

FIrst do this:

Syncing to a "New" Computer or replacing a "crashed" Hard Drive: Apple Support Communities

If you have a 2G iPod and do the above on a computer with iTunes 10 or later the iPod will be udate to 4,2,1, the last update for the 2G.

If you have a 1G, ge here to get the last update for the 1G

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

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