某日,突然发现WM5.0的手机在插入usb线连接到PC后，没有象通常样子ActiveSync自动连接。
排除了是因为ActiveSync设置改变原因后，点击ActiveSync没链接成功的对话框中的帮助，得到如下测试结果：

要使电子邮件、日历约会和联系人与 PC 同步，必须安装 Microsoft Outlook XP (或更新版本)
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无法获得设备的 IP 地址。要获取有关 IP 地址常见问题的最新解决方法，请单击以下链接:
http://go.microsoft.com/fwlink/?LinkId=65461
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无法建立 PC 与设备的连接。要获取有关连接常见问题的最新解决方法，请单击以下链接:
http://go.microsoft.com/fwlink/?LinkId=65257
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没有发现其他未知问题。
如果您仍遇到问题，请将结果发送给 Microsoft 以改进以后的版本。
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于是点击http://go.microsoft.com/fwlink/?LinkId=65257 进入看到答案：原来是因为某次系统优化中，关闭了Dhcp Client 服务造成。启动后Dhcp client service后，一切恢复旧秩序。

If the DHCP Client Service on the Computer is Not Running

The Windows Dynamic Host Configuration Protocol (DHCP) Client service is used to assign an IP address for device-to-computer communication. If this service is not running correctly on your computer, ActiveSync cannot start device-to-computer communications.

关键词： Windows Mobile 5.0 ActiveSync DHCP Client Service