how do I get my music from my old computer to my new one?

When your iPod is set to sync automatically you just need to take care connecting to an empty iTunes. You can use a keyboard command to prevent your iPod auto-syncing with iTunes. While connecting the iPod to the computer on Windows with iTunes installed hold down the Shift + Ctrl keys together. This will stop the iPod from auto-syncing with iTunes and the iPod will appear in the source list. Wait until you are sure the iPod has mounted, and that it will not auto sync and then you can let the keys go. This may take between 20 to 30 seconds depending on your computer: iTunes - Keyboard Shortcuts for Windows

Alternatively open iTunes first and go to Edit>Preferences>Devices and check the box "Disable automatic syncing for iPhones and iPods" and choose Ok. Then connect your iPod.

If at any point you get the message that your iPod is linked to another library and asking if you want to link to this one and replace all your songs etc, press "Cancel". Pressing "Erase and Sync" will irretrievably remove all the songs from your iPod.

iTunes will only let you copy your iTunes Store purchases directly from an iPod to the computer, you'll find details in this article: Copying iTunes Store purchases from your iPod or iPhone to a computer

Purchased applications can be downloaded over again, see this article for details: How to redownload purchased applications from the App Store

For everything else (music from CDs, other downloads and including iTunes purchases) there are a number of third party utilities that you can use to retrieve the music files and playlists from your iPod Touch or iPhone. You'll find that they have varying degrees of functionality and some will transfer data (such as playcounts and ratings), movies, videos, photos, podcasts and games as well.

A selection of iPod/iPhone to iTunes utilities:
Senuti Mac Only (iPod Touch & iPhone compatible)
SharePod Windows Only (iPhone and iPod Touch compatible)
TuneJack Windows Only (iPhone and iPod Touch compatible)
iPodRip Mac & Windows (iPhone and iPod Touch compatible)
Music Rescue Mac & Windows (iPhone and iPod Touch compatible)
iPod Music Liberator Mac & Windows (iPhone and iPod Touch compatible)
iGadget Mac & Windows (iPhone and iPod Touch compatible)
iRepo Mac & Windows (iPhone and iPod Touch compatible)
iPod Access Mac & Windows (iPhone and iPod Touch compatible)
TouchCopy Mac & Windows (iPhone and iPod Touch compatible)

i recently got a new computer aswell and i used an easy transfer cable to transfer all my files and settings from my old xp computer to my new vista computer. it takes a while but it's a lot easier than doing it manually.