NTOSKernel.exe file is missing

Here is the complete procedure for this.
1) Take out the crashed windows XP machine hard disk
2) Make it secondary hard disk in your another Windows XP machine.
3) Copy ntoskernel.exe file in secondry harddisk rootdrive:\windows\system32 folder from your rootdrive:\windows\system32 folder.
4) Remove secondary hard disk and attach it in its original machine.
5) Try to boot your computer now. It should get booted without any issue.