Sleep is not Off. During sleep, the pc is actually still running, just in a low power mode where non-essential components are shut down or turned down so low as to be looking shutoff. Kinda like when you sleep, subconscious is still working but conscious thought is not, your heart still beats and you still breathe. In order for the mouse/kb to wake the pc, it needs to still be on, if the mouse is off, it'd not know you are moving it. Since the pc is technically still on, the fans might slow down but not stop entirely or the pc would overheat. If the fans have leds, they will still be on, as power is still fed to the fan, the leds are rarely separate, and those that are are switched manually, not by the cpu.
There is only 1 fix to turning everything off, and thats turning the pc off completely. Sleep is a low power mode, not a dead mode.
Hibernation is for laptops. Not desktops. Turn it off and get rid of it entirely.
http://www.sevenforums.com/tutorials/819-hibernate-enable-disable.html