The computer's serial number can be very useful.  Among other things, many manufactuers' support sites keep record of their machine's serial numbers to serve the right drivers for downloads.

CMD> wmic bios get serialnumber

Wmic is the command line executable for performing simple WMI queries.  BIOS is wmic's shorthand for Win32_bios.  The PowerShell equivalent would be

PSH> (Get-WmiObject win32_bios).SerialNumber

On the production machines I work with, some do not have PowerShell installed. This being a production environment, installing PowerShell is not an option, so the wmic alternative is welcome.