I've learned that this bitmap is contained in a compiled form in either a DLL or EXE file, which could be decompiled and modified, but I'm not sure which file it is. Can this apply to Windows XP as well?
This is more complicated than it was in Windows 98, which is probably what you heard about. You have to change the resources within the kernel file, Ntoskrnl.exe. For step-by-step instructions, see the article at How to change the Windows 2000 boot logo.
This was first published in June 2003