Well this KB is new to me, but worth pointing out anyway especially if you have a solid colour as your desktop background.
The Welcome screen may be displayed for 30 seconds during the logon process after you set a solid color as the desktop background in Windows 7 or in Windows Server 2008 R2
Applicable to Windows server 2008 R2 as well.
Of course solid coloured backgrounds are boring so go get yourself a cool Windows 7 theme or background image.
For more information on speeding up your computer try the following.
Originally spotted on Softpedia