Macbook Screen gray

[Wild42]

my Daughter's Mac book goes to the Screen with Apple Logo then the logo turns to a Circle with a line throo it it say something Error Loading Kernel Mach-Kernel (0x12)
i got some info and it say to reinstall the Disc i dont have the Disc so what can i do

 

[Satcomer]

Try the steps in the Apple document Resolve startup issues and perform disk maintenance with Disk Utility and fsck and see if your internal hard drive went south without you.