Can't get rid of this Do thing

Every once in awhile a blue box pops up in the middle of my screen. I've determined it is Gnome Do. Nothing I do can get rid of it other than rebooting. while it is running I can't do anything else. Even if I reboot it usually pops back up into the middle of the screen. It seems to be pointless and taunts me by asking me to type something. I've tried removing it but it says other programs need it. I've never seen a program like this that takes over the computer and does not let me do anything. I need to stop it from doing this. I'm not some sort of Linux propeller head, so keep it simple. I just like Gnome because it is more stable than the Windows Vista OS that was running on this laptop. It is really annoying when it happens when one of the other family members gets it and insists on calling me at work to complain. The little triangle in the upper right corner is ineffective and there is no stop button. god.