This may help (can't recall exact source):
Disabling the blue Welcome screen and startup/shutdown messages:
Change from the default windows XP welcome screen to the older style by going to Control Panels>User Accounts>Change the way users logon or off. Deselect the "Use Welcome Screen" checkbox.
To get rid of the startup and shutdown messages via regedit:
HKEY_LOCAL_MACHINE>Software>Microsoft>Windows>CurrentVersion>Policies>System
If there's a DisableStatusMessages dword there, change it to 1, otherwise add it and change it to 1.