In Windows in Libraries\Music\iTunes | On the Mac in Users\<username>\Music\iTunes |
iTunes Library.itl | iTunes Library |
iTunes Music Library.xml | iTunes Music Library.xml |
Here are the steps in detail:
Step 1) Exit iTunes on both computers
Step 2) Locate the 2 files on your primary computer (Where you normally sync your iPhone with iTunes)
Step 3) Copy the 2 files to a USB drive
Step 4) Rename "iTunes Library" to "iTunes Library.itl" or vice versa on the USB drive
Step 5) Locate the 2 files on your second computer and make a backup copy
Step 6) Copy the 2 files from the USB drive to the second computer
Step 7) Plug your iPhone into the second computer, start iTunes and sync. This step can take quite a while depending on how much data is on the iPhone. Mine took about 10 minutes.
Step 8) (optional) Authorize iTunes