The Value of OEMBackground Registry Key Resets Back to 0 after Theme Gets Changed
SYMPTOMS
You are setting this registry value so that you can see a custom welcome screen background:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\Background]
"OEMBackground"=dword:00000001
However, this registry key resets back to zero after you click, select or create a different theme in the "Personalization" control panel, hence the custom background no longer shows.
CAUSE
When you change the theme in the personalization control panel, it will change OEMBackground to match the value stored in the theme ini file.
RESOLUTION
Windows 7 has new Group Policy options to control it. Please use the following steps to enable custom welcome screen background:
1. Run "gpedit.msc" in a command window.
2. Navigate to "Computer Configuration" -> "Administrative Templates" -> "System" -> "Logon".
3. Enable the policy "Always use custom logon background".
REFERENCE:
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https://social.technet.microsoft.com/Forums/en/w7itproui/thread/2c6973cf-0800-4661-a2c4-2d783a316b01
https://social.technet.microsoft.com/Forums/en/w7itproui/thread/5dc99b7c-17a8-42b1-86b4-0084ffb25a99
https://social.technet.microsoft.com/Forums/fr-FR/win7fr/thread/fe7c1096-61d8-4d1c-8878-822a65fe30f9