low quality boot/logon screens

Running XP SP3.
I just recently had to replace my monitor and have a pretty nice HP with a much higher quality than my previous monitor. I noticed right away that the boot screens and logon screens that I have been using now appear lesser quality, grainy, some minor pixelization.
Where are the boot screens and logon screen kept in the OS? I assume that they are bitmaps that are loaded behind other elements and can be replaced with a higher resolution images?