It's in the Registry -
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce]
"Cuboid Simulation"="C:\\someplaceonyourharddrive\\CuboidSimulation.exe"
Delete this key "Cuboid Simulation"

Everytime you start it up, it puts itself there so when you logon or reboot, it starts back up.
A little nasty trick if you ask me.