i found this. i think its what you are after. i do remember that there are two places to change the logos but i havn't found the second one yet. i've read about it but never really messed with it much so i don't remember off the top of my head. i'll keep looking for the one i was using when i messed with it a while back.. it was a good guide.
Click the Start button and type in the search regedit.exe and load ENTER
Navigating in the window go to HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows \ CurrentVersion \ OEMInformation
If i do not have any information you must create the registry keys REG_SZ
Logo ----- REG_SZ (put this value because of the way for the image)
Manufacturer ----- REG_SZ (put the name of the company that sold the machine, or company that created)
Model ----- REG_SZ (put the model of the machine)
SupportURL ----- REG_SZ (put the link from the support site, the company that sold)
Now you can change the data values.
When you finish EXIT you can just see the properties of the Computer and see if everything is put in as registry keys.
Note: The image of the logo must be in. BMP and maximum size of 120x120 pixels.