Good news: In former times you had to disable System Restore, exchange some dlls n’stuff. Today Windows 7 allows you to change the background of the Logon Screen pretty easy:
It’s only the the following 2 steps:
1) set the value of the registry key from 0 to 1: HKLM\Software\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\Background\OEMBackground (dword)
2) copy the desired new background image [...]

As a .NET Developer:
Ever tried to find out more information about your computer’s system?
Ever needed a list of connected USB-Devices, available Serial Ports or Printers?
Ever heard of WMI?
Did you know, it’s also supported by Mono?
There’s a free tool from Microsoft, which is of great help navigating through namespaces, classes and their properties called “WMI Code [...]

Wird in Windows 7 oder Windows 2008 R2 als Desktophintergrund eine Volltonfarbe festgelegt, wird die Willkommenseite möglicherweise für 30 Sekunden angezeigt.
Das Problem ist bekannt und ich habe den von Microsoft bereitgestellten Hotfix  gefunden.

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