Must have ben a CAT Scan? (Sorry...) You need either a Windows Repair Disk or an Installation disk. Get a friend who has a W8 PC to create a repair disk or download Installation media from http://go.microsoft.com/fwlink/p/?linkid=271128
You'll need your Product Key from the base of your laptop and a DVD or USB drive to create.
If neither is possible you should be able to restore your Laptop to Factory Settings, but you'll probably lose all your personal stuff. (Hit F4 at Power on...)