Microsoft has incorporated a new feature in Windows 7, which allows OEMs, and in turn the end user, a way to change the logon screen background without using any hacks or third-party tools. Windows 7 now supports customization of the Windows 7 logon screen officially! Replacing the old logon screen is just another task like changing the wallpaper.
Thanks to Rafael from withinwindows for finding this feature.
Follow the procedure below to change the Windows 7 logon screen.
2. Now, head over to the following folder:
If it does not exist, then create a new folder named Info. Now, open up the Info folder and create another folder and name it as backgrounds.
3. Copy your favorite image file to this folder and rename it as backgroundDefault. The image must be in the JPG format and less than 256 KB in size.
4. Reboot your system and enjoy your favorite background.
The following files (sorted by width-to-height ratio) are supported in the %Windows%\System32\oobe\Info\Backgrounds folder:
The backgroundDefault.jpg image is loaded and stretched-to-fit when a resolution/ratio-specific background cannot be found. If the background cannot be loaded (e.g. image physically too large, incorrect ratio, etc.), the default SKU-based image is loaded.
How it works:
First, a check is made to determine if the customization functionality is enabled or not. To be more precise, a DWORD value named OEMBackground in the HKLM\Software\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\Background key is checked. The value defines whether or not this behavior is turned on, i.e. 1 for enabled, 0 for disabled. This KEY may not exist by default, depending on your system.
If customization is enabled, the primary monitor's screen height and width are retrieved via calls to GetSystemMetrics. These values are used in the computation of the screen width (w)/height (h) ratio. For example, a desktop resolution of 1920×1200, the ratio, computed by the division of w/h, is 16:10 (1.6:1).
The result of this computation, is looked up in an internal table, which determines what image to load on disk. It appears resolutions higher than 1920×1200, will force the loading and zooming of an image of closest compatibility (e.g. same ratio, smaller image).