Windows 7 Disappeared?

The Dell Inspiron, with Windows 7, we bought our daughter last year worked fine until she left last May for an internship. We ran scan disc before the lap top was packed. When she arrived at her destinaction it did not work. According to the Geek squad, the hardware works fine, but there is not an operation system on the laptop. The laptop did not come with discs, but it has the Windows 7 label on the back with the product code. But when emailing Micrsoft support, they only want the PID which can't be retrieved from a computer that doesn't have an operating system.