Syncing an old iPod touch with a new computer

Welcome to the discussions,
Due to the change of your computer, iTunes will erase your ipod during the first sync and replace all content with the content of the new iTunes library. To be able to save your data and settings on your phone, back up manually before.
Authorize your new iTunes in the Store menu. Disable autosync in iTunes/settings/devices, connect your ipod to your new computer and right click on it in the device list and choose backup. iTunes will backup your phone without syncing.
Do the same to transfer your purchases by choosing "transfer purchases" this time. Apps and bought media will be copied to your library.
When you connect your device for the first time, all media content will be erased. But you can restore your settings and app data from your manual backup afterwards.
Don't forget to set up at least one contact and event on your new computer to be able to merge calendars and contacts when you sync the phone for the first time.

About backups and what's saved: http://support.apple.com/kb/HT1766
How to back up and restore: http://support.apple.com/kb/HT1414
How to download apps for free again: http://support.apple.com/kb/HT2519

Music is one way only, from the computer to your device, unless you bought the songs in itunes and transferred your purchases.
There is 3rd party software out there, but not supported by Apple, see this thread: http://discussions.apple.com/thread.jspa?threadID=2013615&tstart=0

Hey Ingo, where were you when I needed to do this? Too late now. When you say 'music is one-way only, from computer to iPod', does that include podcasts? If so, I'd say be ready to have all of your podcast episodes, records of which you've heard and not heard, and your subscriptions... completely blitzed. This has happened to me on a couple of firmware updates, and when I moved my iTunes account to my new computer. I continue to have problems because I didn't think of backing up without syncing. In fact, given the DRM reasons for the rigid iPod/PC relationship, it never crossed my mind that it would be possible. The two things were probably joined in my mind because in everyday life, backing up is part of the automated sync sequence.

Still. If this were part of Apple's up-front documentation, that would be neat. People get new computers all the time, and for all kinds of different reasons. Someone buying a new iPod might easily be within 2 months of needing a new PC.

Still. If this were part of Apple's up-front documentation, that would be neat.

After you bought a couple of songs or videos in iTunes, I haven't found out yet how many it takes, there will be a message displayed by iTunes, to back up your iTunes library "now" or to "do this later on your own". I admit, I've never used that dialog from iTunes to back up the purchases, because iTunes is included in my computer backup routine.
See also: "Tunes Store: Purchased songs, videos, iPod Games, and albums can be downloaded only once": http://support.apple.com/kb/HT1469

But Apple should develop a way to sycn your ipod with a new computer. After all, Apple is supposed to be all about making computers, and devices easy, right? So they should make this alot easier to do, and alot less worrisome.

You can tell Apple directly using this link: http://www.apple.com/feedback/iphone.html