Check the sticker on the bottom of the laptop
Check the label inside the battery compartment, if removable
Open Command Prompt and run `wmic bios get serialnumber`
Open PowerShell and run `Get-CimInstance Win32_BIOS | Select-Object SerialNumber`
Open System Information and look for the BIOS serial number
Check the laptop box or purchase receipt
Check the manufacturer support app or BIOS/UEFI setup
Visit the manufacturer’s support website and use the device info tools
Check the original invoice or warranty documents