I have used this modification on our demonstration SBS 2003 server. Prior to going out to demo SBS to a new customer, I alter the displayed name to be that of the customer I am going to see. This gives the customer a degree of ownership even before they get the quote for the new system.
1. Run Regedit.
2. Navigate down the tree to the following key: HKLM\Software\Microsoft\Windows NT\CurrentVersion
3. Right click the entry called RegisteredOrganization and select Modify.
4. Enter the new Company name you want to see and press enter.