If you need the serial number from your computer and you, don’t have a sticker, the sticker is too hard to get to, or you just want to do some cool IT stuff, start a CMD (command window) and type:
WMIC BIOS GET SERIALNUMBER
This command is not case sensitive.
It is particularly handy when working with tablets like the Microsoft Surface 3 or Asus T100.
In case you are wondering what wondrous and magical system is responsible for this it is the WINDOWS MANAGEMENT INSTRUMENTATION (WMI).