You receive the "NTOSKRNL Missing or Corrupt" error message at startup.
NTOSKRNL is the heart of the operating system, running as a privileged process with direct access to system data and hardware. With direct awareness of the system hardware, NTOSKRNL extracts information from the Registry to know which device drivers to load and in what order. A virus, boot.ini, or a file system corruption may have made the NTOSKRNL.EXE file unusable. NTOSKRNL gets device information to pass on to the Hardware Abstraction Layer (HAL) driver so the core operating system can function. Replacing the file is an easy sure cure.
Tips for correcting this problem and related issues are available at http://www.computerhope.com/issues/ch000646.htm.