现象：
Windows Server 2008自动更新以后，重新启动系统时，会显示进入第三阶段更新，每次到了99%后（或者，有时会进一步显示“等待Windows Modules Installer...”），就再次重新启动，然后不断自动重复这个过程。即使选择进入安全模式，也是如此。 由于无法登录进入操作系统，就无法卸载更新或者系统恢复（除非使用一键Ghost）。
原因：
经过多次重装Windows Server 2008后测试，发现是“Windows Server 2008平台更新程序(KB971644)”引起。
解决方法：
注意：
1、以下所列方法，不是根本性的解决方法，只是作者经过网上搜索，添加上自己的实践经验而已，欢迎指正！
2、经过网上搜索发现，会引发Windows Server 2008更新后不断重启的更新包，还包括其它的更新包。
3、作者的方法参考以下网址
4、作者解决不断重启的方法，可能源自上面第一个网址提到的Method 3(但是无法在该网址中找到)，具体实现是按照上面第二个网址的答复中的方法。对于第一个网址的Method 1和Method 2，作者没有测试过。
方法一： 停止自动更新
选择手动更新，并在更新时，去掉更新“Windows Server 2008平台更新程序(KB971644)”。
但是，Windows Server 2008会在很多时候自己启动更新服务（如在升级SilverLight时），一不小心，就会自动下载更新，并无法选择去掉更新“Windows Server 2008平台更新程序(KB971644)”。
所以，这个方法更彻底的方式是禁用自动更新服务
方法二： 改变Pending.xml的名称，并修改注册表
此办法简要翻译自上面第二个网址的答复中的方法。如果不幸进入不断重启的地步，请尝试以下方法：
1.插入Windows Server 2008的安装光盘并重新启动计算机；
2.采用光盘启动计算机；
3.配置语言、时间、货币格式后选择下一步；
4.选择修复安装；
5.选择应用修复安装的操作系统；
6.在系统修复的选项窗口中，选择命令行方式；
7.进入C:\windows\winsxs目录，并改变Pending.xml的名称“ren pending.xml pending.old”；
8.键入regedit进入注册表，选择HKEY_LOCAL_MACHINE；
9.在File菜单中选择“加载配置单元”，然后选择“C:\windows\system32\config\components”；在弹出的窗口中输入“Offline_Components”
10.在注册表中，删除以下子项
HLKM\Offline Components\AdvancedInstallersNeedResolving
HKLM\Offline Components\PendingXmlIdentifier
（注：作者没有看到第一个子项）
HKLM\Offline Components\PendingXmlIdentifier
（注：作者没有看到第一个子项）
11.退出注册表；
12.在命令行窗口，输入exit退出；
13.在系统修复的选项窗口中，点击“重启”；
以下是上面第二个网址的解决方法的原文引用：
Rename the Pending.xml file, and then edit the registry
Notes: Read the following important notes before you use this troubleshooting method.
- Use this method to resolve the restart symptom that is described in the "Symptoms" section so that you can back up data before you reinstall Windows. You should use this troubleshooting method only if you intend to back up data and to reinstall Windows.
- Use this method only after you try the other methods.
Note: If your computer is not configured to start from a CD or from a DVD,see the documentation that was included with the computer for instructions about how to continue.
- Use this method only if the computer has no restore points or if you cannot start your computer at a point where the System Restore feature is available.
- After you use this method, the following conditions may exist until you reinstall Windows:
- An update that is being installed may not be installed correctly.
- Windows Update may not function correctly.
- If an update is being installed, you may be unable to stop the installation process.
- You may be unable to enable and disable certain optional Windows features.
- Certain optional Windows features may not function correctly.
- The computer may be in an unprotected state.
- An update that is being installed may not be installed correctly.
- Windows Update may not function correctly.
- If an update is being installed, you may be unable to stop the installation process.
- You may be unable to enable and disable certain optional Windows features.
- Certain optional Windows features may not function correctly.
- The computer may be in an unprotected state.
To rename the Pending.xml file and to edit the registry, follow these steps.
Start Windows and go to the System Recovery options:
- Insert the Windows installation disc in the disc drive, and then restart the computer.
- When you are prompted to restart from the disc, press any key.
- When you are prompted, configure the Language to install, Time and currency format, and Keyboard or input method options that you want, and then click Next.
- On the Install Windows page, click Repair your computer.
- On the System Recovery Options page, click the version of the Windows operating system that you want to repair, and then click Next.
- Use the System Recovery options to rename the Pending.xml file and edit the registry:
- On the System Recovery Options page, click Command Prompt.
- Type cd C:\windows\winsxs, and then press ENTER.
- Type ren pending.xml pending.old, and then press ENTER.
- Type regedit, and then press ENTER.
- Select HKEY_LOCAL_MACHINE.
- On the File menu, click Load Hive.
- Locate the following folder:
C:\windows\system32\config\components
- When you are prompted for a name, type Offline_Components.
- In Registry Editor, locate and then delete the following registry subkey:
HLKM\Offline Components\AdvancedInstallersNeedResolving
HKLM\Offline Components\PendingXmlIdentifier
- Exit Registry Editor:
- At the command prompt, type exit to exit Registry Editor.
- Press ENTER.
- Click Restart.
- When you are prompted to restart from the disc, press any key.
- When you are prompted, configure the Language to install, Time and currency format, and Keyboard or input method options that you want, and then click Next.
- On the Install Windows page, click Repair your computer.
- On the System Recovery Options page, click the version of the Windows operating system that you want to repair, and then click Next.
- Use the System Recovery options to rename the Pending.xml file and edit the registry:
- On the System Recovery Options page, click Command Prompt.
- Type cd C:\windows\winsxs, and then press ENTER.
- Type ren pending.xml pending.old, and then press ENTER.
- Type regedit, and then press ENTER.
- Select HKEY_LOCAL_MACHINE.
- On the File menu, click Load Hive.
- Locate the following folder:
C:\windows\system32\config\components
- When you are prompted for a name, type Offline_Components.
- In Registry Editor, locate and then delete the following registry subkey:
HLKM\Offline Components\AdvancedInstallersNeedResolving
HKLM\Offline Components\PendingXmlIdentifier
- Exit Registry Editor:
- At the command prompt, type exit to exit Registry Editor.
- Press ENTER.
- Click Restart.
本文是转载，谢谢分享，帮我解决了大问题。