Step 1, Networking computers.
If you want to share iTunes videos and music between computers, you need to network PC and Mac first.
If you do not know how to Network Windows with Mac OS X, go there:
Networking Windows (2000/XP/2003*) with Mac OS X (10.3/10.4)
Information you will need to know
1.The IP Address of your PC (Start > Run > CMD {return} > "ipconfig" {return})
2The IP Address of your Mac (Applications > Utilities > Terminal {Run app} > for ethernet connection "ipconfig getifaddr en0" {return} or for wireless "ipconfig getifaddr en1" {return})>
3.The workgroup the PC is in (Right click on My Computer, select Properties, and select the Computer Name tab)
System Configuration
It is important that the account you log in with on your XP system has a password set, if it does not you will not be able to login to your Windows share from OS X. You need to put your Mac in the same workgroup as your Windows PC. To do this open "Directory Access" (Applications > Utilities > Directory Access). Click on the padlock in the bottom left corner to make changes; you will be prompted for your password. If "SMB" is not ticked off, then tick it off. Select "SMB" and hit the "Configure…" button. Now enter the name of your Windows workgroup. In my case the name is "AD".
Setting up the PC to share files
You need to create and share a folder on your PC that you will then access from your Mac. To do this create a folder (or select and existing one) right click on it from Windows Explorer and select "Properties". Select the "Sharing" tab and share out the folder. I'd recommend you use a one word name for the share. For example "Mac", not "Apple Mac Share", it just narrows the risk of complications.
Setting up the Mac to share files
Open "System Preferences" (Applications > System Preferences). Go to "Sharing" under "Internet & Network", and tick off "Windows Sharing", and if it doesn't start by itself, click "Start". This will share out your entire home folder.
If You're running Tiger (10.4), you will also need to click the "Accounts" button and tick off the box next to your account name so that OS X knows to share out your particular home folder.
Step2, Go to preferences, under the sharing tab, enable "Share library..." and "Look for shared libraries..." on both computers.
Select the items you want to share.
It will show up in iTunes' side panel:
To require users to enter a password before they can see your shared items, select "Require password" and enter a password.
You will need to authorize both computers to play purchased content however. You may authorize up to 5 Machines per iTunes Music Store account.
Tips：If you want to share music with other users on your computer ，read this article: iTunes: How to share music between different accounts on a single computer
