Lost my computer

Hello! Thank you for reaching out to us. I am your Dell-Cares contact for order related queries. Unfortunately, our customer service is currently unavailable. We are available Monday through Friday. Please reach out to us on any of these days and we will be glad to assist you. Thanks for being a loyal Dell Technologies customer.

The only way you can is if it was activated with a Microsoft account.  If it was, log into that and lock the computer.