Vista Speech Recognition turns itself back on from being off!

I have a gateway vista tablet and just last week I set up Vista Speech
Recognition. I decided that leaving it on all the time was dumb because it
might misinterpret noises as commands. So I put it on sleep mode, where it
only listens for "start listening" and then it turns back on. That's fine,
mostly. Sometimes I noticed that some noise would reactivate it back on
again. So, I turned it off completely. Or so I thought. So, now, every
once in a while I look over at it and notice that it's back completely on, or
back on in sleep mode.

Is there some voice or key command that brings it back from off mode? I
suppose I could be hitting something accidentally, but even this seems
unlikely. Seems like it either turns back on automatically after a certain
number of minutes, or that it is STILL listening for some command to turn it
back on. I'm close to disabling it entirely. I'd rather not sit down at my
computer one day and come to realize that it's deleted files or text I cared
about, because it was stupid enough to start listening again.