Do you mean the logon screen...on WinXP for example? If so you can use LogonStudio which does that for you............here's da link https://www.stardock.com/products/logonstudio/
Ahhhh, now I see. I know that it's a file hidden away in a root folder somehwere cuz I did manage to change it once to put up a borg boot screen telling me my comp had been assimilated.
/ME looks for his backback and schedules for the short yellow bus to come to house tomorrow