
There are several methods to sharing your
iTunes Libraries across computers in your local network. The easiest method of them by far is for connecting any
Macs in your network, connected by Ethernet or WIFI connections.
Start
iTunes on the computer with the Library you wish to share.

Go to
Preferences. Select the
Sharing pane, and check the "
Share my library on my local network" box. Along with checking "
Look for shared libraries" for good measure. You can then decide if you want to share your music, movies, etc. or all of your Library.
Now, on your other machine, start up
iTunes. You should be able to see the username of the computer with the shared Library in the left side along with your Library and Playlists.
If you do not see the Shared Library listed, or you try to connect to the Library and it does not fully connect. Go to
Preferences, under the
Sharing pane make sure you have the "
Look for shared libraries" box checked. If that does not work, go to
System Preferences and depending on your version of OS X, look for
Firewall, or go to
Security and choose the
Firewall pane. Click on "
Set access for specific services and applications". Click on the plus sign and manually add
iTunes.
Now, if you wish to have sharing from your
Mac to
Windows XP machines or a
Windows XP machine to
Macs is not as easy to do if you have a
Firewall enabled. It involves using an interface that is not very intuitive.
After you have enabled Sharing in
iTunes as written above, you want to do the following on both the
Windows machine hosting or receiving the iTunes Library:
Click on the
Start button, then go to
Control Panel. Click on
Network Connections.

Double-click on the Ethernet or Wireless connection that you use. Click on
Properties, then click the
Advanced tab, then click
Settings, and click
Advanced, and then select your internet connection (wifi or ethernet) and finally choose
Add. Type "iTunes Sharing" for the description. Both Internal and External Ports should be 3689. Select TCP. Click OK to close.
Now Add one more Service. Name the description "Multicast DNS". Both the Internal and External Ports should be 5353. Select UDP. Now click OK for the Service, then click OK again and exit.
Now your
iTunes Library will show up on the left side of your
iTunes in
Windows XP or the
Mac on the local network.