Check the bottom of the laptop for a sticker or engraved serial number
Open the battery compartment if the battery is removable and look for the serial number label
Check the original box or packaging for the serial number label
Look in the BIOS or UEFI setup screen during startup
On Windows, open Command Prompt and run `wmic bios get serialnumber`
On Windows, open PowerShell and run `Get-CimInstance Win32_BIOS | Select-Object SerialNumber`
On macOS, click the Apple menu, select About This Mac, and note the serial number
On Linux, run `sudo dmidecode -s system-serial-number`
Check the manufacturer’s support app or system information utility
Sign in to the manufacturer’s website and check registered devices
Check the purchase receipt, invoice, or warranty card
Contact the manufacturer’s support team with the laptop model and proof of purchase