In a partnership, content can be synchronized automatically or manually between one user's library on one computer and one device. Windows Media Player can support up to 16 synchronization partnerships, which means that you can synchronize content in your library to 16 different devices that you connect to your computer.
When you connect your device to your computer for the first time, Windows Media Player starts the Device Setup Wizard, which helps you create a partnership between the Player and your device. When you establish the partnership, you must specify whether content in your library will be synchronized to your device automatically or manually. If you specified automatic synchronization, your device will be synchronized every time you connect it to your computer or change synchronization settings (for example, add or remove a playlist to be synchronized) for the device. If you specified manual synchronization, then every time you connect your device to your computer, synchronization will not start until you select the content and specify the order in which it is synchronized.
If you connect a device that already has a partnership to a different user's library, the Device Setup Wizard offers to use the device with the new library for the current session, or switch the device’s partnership to the new library permanently.
If you do not switch the partnership to the new library, certain features are disabled, such as synchronizing updated ratings and play counts. Also, content that is synchronized to the device during the current session cannot be managed later by the Player that maintains the partnership with the device. If you need to delete this content to free space on the device, you must do so manually.
If you switch the device's partnership to the new library permanently, the content synchronized to the device from the previous partnership, or any other content stored on the device, remains on the device and can still be played. However, this content reduces the amount of space available for storing synchronized content under the new partnership. To delete content left on a device from a previous partnership, click the device in the Items on Device pane (the right side of Sync), select the content on the device, and then click the Delete button .