Want to change your boot screen without patching your actual OS kernel?
Stardock has a free program in development to do just that and the first alpha is now available:
http://scripting.stardock.com/private/bs_current.exe
BootSkin replaces the boot screen by creating a device driver that does the job. This has several advantages:
1) It will work on Windows 2000, it'll work on Windows XP, and it'll work on Longhorn 4051 it seems to work. Heck, it probably works on NT 4.
2) This has been implemented in the way that Microsoft would probably do it (or arguably how they should have done it). No patching, no hacking, totally safe.
3) No need to "back up" your kernel. If you somehow blow up your system, you can just boot up in safe mode and uninstall it.
Limitations:
Right now it's no better no worse than the regular boot screen. That means 16 color VGA (640x480).
What's next:
High resolution, true color and animation. But this is just to get things started and make sure there aren't any problems. It's been tested extensively internally but usual caveat: This is an alpha, use at your own risk, assume it will blow up your computer, kill your pets, set the house on fire, etc.