Removing Windows Branding(Logo) from logon screen
from 
WinCustomize Forums
WinCustomize Forums
Logo can be removed...with a program called resource hacker:
run resource hacker
navigate to C:\Windows\Branding\Basebrd
Open Basebrd.dll
Locate the bitmap Folder Then delete bitmaps.
Note: You can Change/Edit the bitmap also.
Been without the logo for months and doing this had no adverse affects on vista.