search for kill.exe os PSTools (pskill.exe)
In Task manager, in the Processes tab you have to add the PID column. The kill (or pskill) program will need the Process ID number as a parameter.
PSTools package also has pslist to get a list of processes.
http://technet.microsoft.com/en-us/sysinternals/bb896649.aspx
These programs will also kill/stop processes which Task Manager will cannot (such as returning an access denied message).