Windows 7 and Windows 2008
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
http://support.microsoft.com/kb/977346/en-us
Windows XP and Windows 2003
![我的职业生涯（四）[图]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)