刚才帮一个同学装系统，轻车熟路地把XP光盘放入光驱，重启，安装系统（从光盘拷贝文件到硬盘时提示缺少一个文件，当时也没多想，以为只是D版光盘质量不好，少个文件也没什么，直接按钮ESC就跳过了），一切似乎都很正常，当完成注册进入XP时，电脑跳出个对话框，提示“Windows产品激活，一个问题阻止Windows正确检查此机器的许可证。错误代码：0x8007000”，按了确定后又退回到登录框，点击用户列表登录时又提示错误，如此反复，简直莫名其妙。
原来从没遇到过这种问题，也不知道怎么解决，以“0x8007000”为关键字在google中搜索，在微软客户帮助和支持主页查到一篇文章，按着做，还是解决不了问题，只有继续搜索。
又找到一篇文章，内容如下：
When you start Windows XP and log on, your receive the subject error. When you press OK, you are returned to the Log On to Windows dialog.
NOTE: If you perform a System Restore, the problem may persist.
This behavior will occur if you are missing the %SystemRoot%\System32\secupd.dat file and / or the %SystemRoot%\System32\oembios.dat file.
To resolve this problem:
1. Restart your computer and press F8 to start in Safe Mode.
2. Log on.
3. Right-click My Computer and press Manage.
4. Open the Event Viewer.
5. Check the System event log by using the View menu to Filter for an Event source of Windows File Protection since the last time you successfully logged on. You should be able to locate the files that could not be found during logon, probably as Event ID 64005.
6. Using another Windows XP computer, preferably as the same service pack and hotfix level, copy the missing files. If you don't have another Windows XP computer, you may be able to Expand the missing files from the Windows XP CD-ROM.
7. Restart your computer normally.
8. You may have to reapply the latest service pack and hotfixes, perform a SFC /SCANNOW and also check for viruses and other malware.
按照上面的步骤来，发现在安全模式一下根本没法执行SFC命令，不过到提醒了我，这个问题应该是缺少安装时跳过的那个文件所造成的，和另一台可以启动的电脑的%SystemRoot%\System32\目录仔细对比了一下，发现有问题的那台少了oembios.bin，有12M的样子，用U盘拷过去后，问题解决了！