login dialog box in windows 2003

I have windows 2003 after the system reboots startup screen is partially displayed (alt ctrl del screen) i cannot view properly its just reads windows 2003 when i press alt ctrl del i can see blank screen with cursor blinking and blindly enter user name and password it works and screen becomes normal i can view all my icons, my question is how do i make alt ctrl del screen fully viewable i have already ubinstalled and reinstalled video drivers and also system running latest patches.its dell 2450 server,
login dialog box where we enter username and password is not visible.