My friend's Sony Vaio laptop is missing
<Windows root>\system32\ntoskrnl.exe
Please re-install a copy of the above file

Is this something I can simply pull from a boot disk?

Other symptoms. His machine will not start up in normal or safe mode. His local profile was already corrupt before this point. He had a virus that he thinks he cleaned up but I know how deceptive they can be. Could this be the virus coming back? Or is this a lack of maintainence, defrag? Any help?

Yes It is mostly happens due to following reasons:
-> 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.

You need to recopy ntoskrnl.exe to system32 directory.

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.

hope u will get it. Gud luck!

If you have an XP Pro install disc, you may want to do a repair installation:
http://www.microsoft.com/windowsxp/...
The only thing you'll have to do after the installation is re-load all the critical updates.

Some HELP in posting on Cnet plus free progs and instructions Glad to Help!