Where is the software that can display the blessing slogan as soon as the computer is turned on?

You can try the boot prompt information that comes with XP first to see if it can meet your requirements.

Run secpol.msc, and then click Local Policy => "Security Options".

In the right pane, locate Interactive Login: Message Title of User Trying to Login.

This is the title. Double-click it to set it as: bless you;

In the right pane, locate Interactive Login: Message Text of User Attempting to Login.

Double-click and type what you want to prompt, such as "Happy Birthday".