Actually, there is no way to copy music from your iPod to your computer officially. There are programs out there that will let you do this, but it is not from Apple.
On my iPod Touch 2G and iPhone 4, I have installed an app through Cydia called "myTunes." Basically, myTunes will put your music in the directory "var/mobile/media/myTunes." Then, using SSH, you can copy these music files back to your PC.
The only downside to this is that you have to jailbreak (not really a bad thing, but it takes time to do sometimes) and that you have to deal with sending stuff wirelessly to your PC (the speed of this depends on the connection, but it'll take some). A better way is to actually downgrade a program that will allow you to do this. You will need to look these programs up on Google to decide which is best for you.
I hope this helps!