Please take the following steps to replace Logon UI logo.

1. Click Start, type Regedit and press Enter

2. Navigate to

HKLM\Software\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\Background

3. Change value of OEMBackground to 1.

4. Now navigate to %windir%\system32\oobe, create folder “info”, double click it and create another new folder “backgrounds”

5. Now place your desired logon file into %windir%\system32\oobe\info\backgrounds

6. Rename the file to backgroundDefault.jpg. (Please NOTE: Images must be less than 256kb in size).