Can't kill task

Hi!

I have a game, that, after closing remains in memory. By no means am I
able to end this task (with taskmanager)
I also tried a tool named "killprocess" which is supposed to do the
same. However when I end the Task it appears again and the only way to
get rid of it is to rebot which is of course not the preffered
solution.

Does anybody know another way of killing nasty applications?

Thx!