Do Son 
Users of Windows 7 or Windows Server 2008 may have encountered an issue wherein setting the desktop background to a solid color (through the personalization settings, rather than selecting a solid-color image) results in a noticeable 30-second delay upon startup before the desktop fully loads.
The root cause of this problem lies not in the color choice itself, but in the distinction between using a true solid color versus an image — even a solid-color image does not trigger the delay. The underlying issue stems from a flaw in Microsoft’s code, a defect that introduces this startup lag when certain conditions are met.
Microsoft engineer Raymond Chen recently illuminated the technical reasons behind this behavior in a detailed blog post.
According to Chen, during the Windows NT logon sequence, multiple components — including the taskbar, system services, desktop icons, and background — must all signal readiness before the welcome screen fades and the desktop is rendered. However, a specific function responsible for indicating that the wallpaper is ready fails to send this signal when the background is set to a solid color. This function is only triggered when an image is used as the wallpaper; when a solid color is selected, the function is entirely bypassed.
As a result, the system remains in a state of anticipation, waiting for a readiness signal that never arrives. Only after a 30-second timeout does the system abandon the wait and proceed to display the desktop. Similar issues can arise if group policies are configured to hide the desktop background, as this too may prevent certain readiness signals — such as those confirming desktop icon availability — from being dispatched.
It’s important to note that the system is not actually requiring an additional 30 seconds to complete its startup tasks. Rather, the welcome screen remains visible for the duration of the timeout simply because one component has failed to declare itself ready, despite the likelihood that all other components have already finished loading.
This behavior is, without question, a software bug. Microsoft addressed the issue in November 2009 by releasing a patch for both Windows 7 and Windows Server 2008 R2. Once the fix is installed, setting a solid color background no longer results in startup delays.
