（注：如欲速或准确方法，请跳读STEP3）
刚刚把桌面收拾的一尘不染，突然又想把登陆界面改成和桌面呼应的背景图片，于是：悲剧开始了 - -、
STEP1:注册表
百度知道答案：HKEY_USERS\.DEFAULT\Control Panel\Desktop下某键改为路径。。（无此键）
HKEY_USERS\.DEFAULT\Control Panel\Colors下background键值改路径（=。=不懂）
STEP2:文件修改
无意间发现了登陆背景图片的藏身之处：c:\Windows\System32\oobe\background.bmp
I.直觉就是直接找个图片覆盖（失败，需要权限）
II.Win+R cmd 用DOS环境来复制一次试试（失败）
III.进另外一个系统来修改这个文件，于是Ubuntu光盘面安装启动（失败，不支持的磁盘类型）
中途又临时学了下U盘制作启动盘，最终辗转借来U盘装上PE..（失败，PE系统下依然要权限=。=）
（注意：运行oobe下的程序会出现问题。）
STEP3:准确搜索，关键词"oobe background”
眼前一亮,that's the one！！！
Change Background Image of Logon Screen in Windows 7 by Harshad on March 20, 2009
译 Crazy Ant
Share Tweet
Changing logon screen of Windows Operating System is little tough task to do. So, people prefer third party applications to change the background image of logon screen in Windows XP and Windows Vista.Windows 7 Build 7057 has various interesting features and one such feature in this build is, changing the background image of logon screen in Windows 7.
Yes! It is possible to change the default logon screen in Windows 7 operating system. Rafael from Withinwindows has discovered a hack which allows you to change logon screen in Windows 7. Now, you don’t have to search for logon screen background image changer or any other third party tool. Simply follow the tutorial given below and stay away from malicious softwares.
Change Background Image of Logon Screen in Windows 71.Open RUN Window using WIN+R and type Regedit. 用WIN+R组合键打开打开“运行”窗口，输入"regedit”（打开注册表编辑器）
2.Search for following registry key - 3.HKLM\Software\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\Background 寻找上述注册表项（其中HKLM=HKEY_LOCAL_MACHINE）
4.Change the value of OEMBackground to 1. 修改OEMBackground的键值为"1”
5.Set your custom image in %windir%\system32\oobe 将你喜欢的图片放到C:\Windows\System32\oobe这个目录下
6.Create a folder called “info” in same directory and create one folder named “backgrounds” in info folder so that we can follow the path given in next step. 在这个目录下新建一个文件夹，命名为"info” ，在新建好的文件夹info中建立文件夹"backgrounds”备用
7.%windir%\System32\oobe\info\backgrounds 打开"backgrounds”文件夹
8.Add an image of your choice in backgrounds folder and name the image as backgroundDefault.jpg Files that are supported in this folder are as follows:
添加你喜欢的背景图片到"backgrounds”文件夹并把他们重命名为以下名字中的一个：
backgroundDefault.jpg background768×1280.jpg (0.6) background900×1440.jpg (0.625) background960×1280.jpg (0.75) background1024×1280.jpg (0.8) background1280×1024.jpg (1.25) background1024×768.jpg (1.33-) background1280×960.jpg (1.33-) background1600×1200.jpg (1.33-) background1440×900.jpg (1.6) background1920×1200.jpg (1.6) background1280×768.jpg (1.66-) background1360×768.jpg (1.770833-)
Even though it is possible to change background image of logon screen, we can’t add an image of size more than 256 kb.