Win NT/2000 is a thread based Operating System and not process based Operating System like Unix. Oracle user and background processes are not multiple processes but, threads with in oracle.exe process. 'orakill' is oracle provided utility to kill a particular resource intensive thread under oracle.exe process. For help type in at the DOS prompt C:\>orakill /?
The following query can be used to get the sid, thread id of a particular resource intensive thread.
SQL> select sid, spid as thread, osuser, s.program
2 from sys.v_$process p, sys.v_$session s
3 where p.addr = s.paddr;