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I understand you are getting error ntoskrnl.exe missing on your PC.
Don't worry I'll try to help you out.
Did you make any hardware or software changes on your PC?
Did you know WinXP isn't supported by Microsoft anymore as it's obsolete?
As you mentioned you are getting error ntoskrnl.exe missing on your PC.
Try the steps recommended below.
This error prevents Windows XP from opening. This problem has to be addressed from a command prompt environment.
Use the following steps to open a command prompt environment:
Turn on the computer and press the F8 key repeatedly when the first screen displays.
The Windows Advanced Options menu displays.
Use the Up and Down Arrow and Enter keys to select Return to OS choices.
Select Microsoft Windows Recovery Console.
If Microsoft Windows XP Recovery Console is not listed, restart the computer with a Windows XP CD, Recovery Console CD, or Recovery Tools CD in the top CD or DVD drive and open Microsoft Windows Recovery Console. If a Windows XP Setup screen displays when using Recovery Console CDs, press the R key to open the Recovery Console.
If Microsoft Windows XP Recovery Console is not listed and you do not have a Recovery Console CD, try the following:
Turn on the computer, and press the F10 key repeatedly at the first screen.
At the Recovery screen, click Advanced Options.
Press the Alt + D keys at the same time to open a command prompt window. Then skip to Step 5.
When the login prompt displays, press the number next to the Windows version (minint or Windows) and type the login password. Try pressing Enter if you do not know the password.
At the command prompt, type the following: diskpart
Press Enter, and do one the following:
If a table of volume names displays, remember the drive letter next to the main drive volume name (usually D or H next to HP_PAVILION or PRESARIO), and press the Esc key.
If diskpart prompt displays, type list volume, press Enter, remember the drive letter next to the main drive volume name (usually D or H next to HP_PAVILION or PRESARIO), type exit when done, and then press Enter.
Refer this article to further troubleshoot Ntoskrnl missing on your PC.
If the issue persists after trying out the steps. You have to perform a recovery using the recovery kit.