How could I replace my default Bootscreen without installing a program?

[Rip the Jacker]

? Anyone ?

I don't want to install some prog that's gonna hog all my resources like StyleXP/ThemeXP/Aston Shell...

 

[theAnimal]

Replace the ntoskrnl.exe file in safe mode (rename the original) OR add a /KERNEL= switch in your boot.ini either to your existing operating system line or better yet a duplicate thereof.

Make sure you use the appropriate ntoskrnl.exe replacement (ie for no SP, for SP1, or for SP2)