There are two steps to changing your System Properties box appearance, Changing the Text and replacing the logo.
Step 1) Changing the Text
Create a file called oeminfo.ini
Place the file in your C:\windows\system
Open oeminfo.ini in Notepad.
Here's a sample of the text to be added:
Line1="Ultra-X Test Machine"
Modify the text as you see fit.
Save the file.
Step 2) Changing the Logo
Pick or create the art you'd like to use for you logo
Set the background as transparent.
Scale the image to no larger than 180 pixels wide and 114 pixels high.
Save the image as oemlogo.bmp
Place the file in your C:\windows\system directory
Now admire you work by checking your System Properties box!
Provided by MaximumPC Magazine