As the_Jinx said..we need more information on the OS and things you've tried..have you tried using ProKill by the way?I think it was done by White Scorpion from on here...

Here's what it says on the site:

ProKill is a Commandline process-viewer / killer. This program is much more powerful then the Windows taskmanager since it is able to kill even the Windows own processes and services.

http://white-scorpion.nl/Downloads/pk2_1.zip

Hope that helped..cheers