Until everything is in the cloud and you don’t have to take care about this anymore, getting a new computer often means that you need to move your iTunes library manually.
There are a couple tools online, most of the time they’re not as free as they claim, and really it will take you more time to learn how to use these tools than to read the official Apple way of doing it.
So the only thing you need to know really, is go to the Apple Support page and follow the steps.
Now there’s one point where you might get stuck at if you’re using Windows 7, which is step 4 of the “Restoring your iTunes Library backup” section, where they tell you to “Open iTunes while holding down the Option key (Mac) or Shift key (Windows).”
Unfortunately, this won’t work under Windows 7. What you really need to do is:
- locate your iTunes.exe file, which should be in something like C:\Program Files (x86)\iTunes\
- hold shift key
- right clic
- select Open
You should then get the “Choose iTunes Library” popup and be back on track.
Sources: