I have seen system administrators who feels bending the CPU box or rebooting the system are only ways to find out serial number of a machine. In situations where a remote systems serial is required, they do nothing but reaching that machine physically.
Enough doing hard work and be smart, guys; here is a small powershell code which helps you to get serial number of local or remote machine without moving your feet.
PS C:> (Get-WmiObject -computer COMP-A -cl win32_BIOS).SerialNumber
Replace COMP-A with the computer name you want to query and needless to say that you need admin rights to execute this command.
Post in comments section here if you have any questions.