Ntoskrnl.exe still on computer when i have copied a new version

Assuming a couple of things:
1. Your OS is Windows XP
2. This is the error message you are getting -
"Windows NT could not start because the following file is missing or corrupt:
Winnt_root\System32\Ntoskrnl.exe
Please re-install a copy of the above file."

To reinstall notskrnl.exe, do this:

Start the computer by using your Windows XP CD-ROM. Press any key to boot from the CD.

After the setup files are finished loading press R to repair using Recovery Console.

When you are in the recovery console, select the installation to log on to (usually number 1), and then press ENTER.

Login to the Administrator account by typing the password for this account, and then press ENTER.

At the recovery console command prompt, type the following command, and then press ENTER:

For Uni-Processor systems: expand <cd-drive>:\i386\ntoskrnl.ex_ <hd-drive>:\Windows\system32\ntoskrnl.exe
For Multi-Processor systems:expand <cd-drive>:\i386\ntkrnlmp.ex_ <hd-drive>:\Windows\system32\ntoskrnl.exe
Note In these two commands, the <cd-drive> placeholder represents the drive letter of your CD drive, and the <hd-drive> placeholder represents the drive letter of the hard disk on which windows is installed.

If you receive a prompt to overwrite the file, press Y.

Type exit, and press ENTER at the command prompt.

You should now be able to boot up properly.

1. Insert the Windows XP startup disk in the floppy disk drive, or insert the Windows XP CD in the CD drive, and then restart the computer.
2. Click to select any options that are required to start the computer from the CD drive if you are prompted to do this.
3. When the "Welcome to Setup" screen appears, press R to start the Recovery Console.
4. If you have a dual-boot or multiple-boot computer, select the installation that you want to access from the Recovery Console.
5. When you are prompted, type the Administrator password. If the Administrator password is blank, press ENTER.
6. At the Recovery Console command prompt, type the following lines. Press ENTER after each line. cd system32
   ren ntkrnlpa.exe ntkrnlpa.old
   ren ntoskrnl.exe ntoskrnl.old
   cd "c:\windows\driver cache\i386"
   expand sp2.cab -F:ntkrpamp.exe c:\windows\system32
   expand sp2.cab -F:ntkrnlmp.exe c:\windows\system32
   cd c:\windows\system32
   ren ntkrpamp.exe ntkrnlpa.exe
   ren ntkrnlmp.exe ntoskrnl.exe
   
7. Type exit to quit Recovery Console. Your computer will restart.

Or go to http://www.ventrilo.com/dlprod.php?id=1 and click on agree.

ntoskrnl.exe is the kernel file, the core of Windows. If it's missing your only option is to do a Repair install.

Please follow this step

1. Start the computer by using your Windows XP CD-ROM. Press any key to boot from the CD.
2. After the setup files are finished loading press R to repair using Recovery Console.
3. When you are in the recovery console, select the installation to log on to (usually number 1), and then press ENTER.
4. Login to the Administrator account by typing the password for this account, and then press ENTER.
5. At the recovery console command prompt, type the following command, and then press ENTER:
   
   For Uni-Processor systems: expand <cd-drive>:\i386\ntoskrnl.ex_ <hd-drive>:\Windows\system32\ntoskrnl.exeFor Multi-Processor systems: expand <cd-drive>:\i386\ntkrnlmp.ex_ <hd-drive>:\Windows\system32\ntoskrnl.exe Note In these two commands, the <cd-drive> placeholder represents the drive letter of your CD drive, and the <hd-drive> placeholder represents the drive letter of the hard disk on which windows is installed.
6. If you receive a prompt to overwrite the file, press Y.
7. Type exit, and press ENTER at the command prompt.

It's almost always best to do a clean install when installing a new OS, otherwise these sorts of problems can unfortunately happen.

You should be able to download that file from microsoft, or try googleing "ntoskrnl.exe"
I done it for a missing dll file and found many places to download for free.

Do you have a Windows CD that came with your computer? If so do you know how to boot from it by inserting it into the drive and then pressing F12 just after you switch on your PC? If you can do this then you could try the "repair" option from Windows Setup, this might fix your missing PC problem.

Use the ERD disk and repair the installation. Choose to replace all files, and then replace only the Hal.dll and Ntoskrnl.exe files.

If you can start another installation of Windows NT on the same computer, you can expand the correct Hal.dll and Ntoskrnl.exe files from the Windows NT CD-ROM. To do so, follow these steps:

1. Boot to the working version of Windows NT.
2. Start a command prompt.
3. Change to the CD-ROM drive.
4. Change to the appropriate folder on the CD-ROM (for example, I386 for Intel-based computers).
5. Type expand hal.dl_ <systemroot>\system32 where <systemroot> is the path of the non-functioning Windows NT folder.
6. Type expand ntoskrnl.ex_ <systemroot>\system32.
7. Restart the computer into the other Windows NT installation.

NTLDR is missing  Press Ctrl Alt Del to Restart

----Windows XP users Insert the Windows XP bootable CD into the computer. When prompted to press any key to boot from the CD, press any key. Once in the Windows XP setup menu press the "R" key to repair Windows. Log into your Windows installation by pressing the "1" key and pressing enter. You will then be prompted for your administrator password, enter that password. Copy the below two files to the root directory of the primary hard disk. In the below example we are copying these files from the CD-ROM drive letter, which in this case is "e." This letter may be different on your computer.
copy e:\i386\ntldr c:\ copy e:\i386\ntdetect.com c:\
Once both of these files have been successfully copied, remove the CD from the computer and reboot.

NTOSKRNL.EXE is missing or corrupt.

Related errors:

Below is a listing of the full error message that may be related to this error.

Windows NT could not start because the below file is missing or corrupt:
C:\Winnt\System32\Ntoskrnl.exe

Cause:
Keyboard issue
Miscellaneous corruption
Corrupt boot.ini file.
Missing boot.ini file.
Missing or corrupt ntoskrnl.exe file.
Windows NT installed on a partition bigger then 7.8GB
Corrupted hard disk drive or severely corrupted Windows.
Solution:
Keyboard issue
This issue has also been known to be caused by a short in the ground wire in the keyboard cable. Make sure this is not the cause of your error by replacing the keyboard with a different keyboard or simply just disconnecting the keyboard from the computer.

Miscellaneous corruption
Before trying any of the below recommendations it's recommend that you attempt to load the last known good configuration. Additional information about doing this can be found on document CH000626.

Corrupt boot.ini file
This issue is often caused when the boot.ini is missing or improperly configured. This issue often arises after a user has recently added or removed an operating system on the computer or added or removed hard disk drives in the computer.
Make sure the line pointing to the operating system and it's drive and partition is properly configured in the [boot loader] and [operating systems] section. Additional information about boot.ini can be found on document CH000492.

Missing boot.ini file
Microsoft Windows XP users:
If the boot.ini is severely corrupted or missing a user running Microsoft Windows XP can rebuild the boot.ini to resolve this issue. Additional information about rebuilding the boot.ini can be found on document CH000648.

Microsoft Windows NT and Windows 2000 users:

To restore the original boot.ini file in Microsoft Windows NT or Windows 2000 you will need an ERD and follow the below steps. If you do not have an ERD you will be unable to follow these steps.
Boot the computer with your Windows NT three setup diskettes or the Windows 2000 setup disc.
In the setup menu, type R to start the repair.
When prompted for the ERD diskette insert the diskette and inspect the startup environment.
Missing or corrupt ntoskrnl.exe file
If the ntoskrnl.exe file is corrupt or missing this can also generate the error. To restore this file follow the below steps.
Insert the Microsoft Windows XP CD. Note: If you have a recovery CD or a restore CD and not a Microsoft Windows XP CD it is likely the below steps will not resolve your issue.
Reboot the computer, as the computer is starting you should see a message to press any key to boot from the CD. When you see this message press any key.
In the Microsoft Windows XP setup menu press the R key to enter the recovery console.
Select the operating system you wish to fix, and then enter the administrator password.
Type expand d:\i386\ntoskrnl.ex_ c:\windows\system32
You will then be prompted if you wish to overwrite the file type Y and press enter to overwrite the file.
Type exit to reboot the computer.
Windows NT installed on a partition bigger then 7.8GB
If you are running Microsoft windows NT 4.0 on a partition larger than 7.8GB this issue can occur if the boot files are located outside this limitation. When this error occurs your computer will have the

error message as shown below.

OS Loader v4.01
Disk I/O error status=00000001
Windows NT could not start because the below file is missing or corrupt: winnt\system32\Ntoskrnl.exe
Please reinstall a copy of the above file.

If your system partition is larger than 7.8GB you will need to delete the partition and recreate the partition to 7.8GB or less. Additional information about this issue can be found on Microsoft KB Q224526.

Corrupted hard disk drive or severely corrupted Windows
Attempt to check the hard disk drive for any errors by running the chkdsk error. To do this follow the below steps.

Insert the Microsoft Windows XP CD. Note: If you have a recovery CD or a restore CD and not a Microsoft Windows XP CD it is likely the below steps will not resolve your issue.
Reboot the computer, as the computer is starting you should see a message to press any key to boot from the CD. When you see this message press any key.
In the Microsoft Windows XP setup menu press the R key to enter the recovery console.
Select the operating system you wish to fix, and then enter the administrator password.
Once at the recovery console type chkdsk /r
Once completed type exit and see if issue is resolved.
If after trying all of the above steps you are still encountering the same issue it's likely that Windows is severely corrupted and it is recommended you attempt to reinstall Windows. Additional information about erasing the computer and starting over can be found on document CH000186.
Finally, if during the Windows installation you encounter errors it's likely that your hard disk drive is bad.