infected C:\WINNT\SYSTEM32\KERNEL.EXE

mY C:\WINNT\SYSTEM32\KERNEL.EXE FILE ON THE NT 40 SERVER IS INFECTED BY A BACKDOOR TORJAN AND THE NORTON FAILED TO CLEAN IT.mY QUESTION IS
A-HOW DO I CLEAN IT OR REPLACE IT WITHOUT EBDENGARING THE SERVER(sql).

THANKS.