corrupted file

when i try to start my computer, i get the following error message “Windows NT could not start because the following file is missing or corrupt,\system 32\nt oskrnl.exe.please re-install a copy of the above file” I slave the hard disk onanother machine and ran chkdsk ,windows detected the corrupted file but did not correct it.I don’t want to format the hard disk,any idea about how to go about it?Need your assistance.