Here are the files needed:

c:\logo.sys = bootup logo 320x400x256colors
c:\windows\logow.sys = please wait while computer shuts down
c:\windows\logos.sys = safe to turn off your computer
c:\windows\system\oemlogo.bmp = computer properties logo
108x72x256colors

c:\windows\system\oeminfo.ini = This file contains:
[General]
Manufacturer=Name
Model=Name

[Support Information] ; Button at bottom-brings up box
Line1=Info
Line2=Etc.

Also, you can change the registered user in your registry:
Start, Run, type Regedit.
Either search for RegisteredOwner (and RegisteredOrganization) or go to HKey_LocalMachine, Software, Microsoft, Windows, CurrentVersion.