Just picking up on a couple of things, firstly due to to the nature of an ATX PC power supply, even if the USB and keyboard/mouse lights are off, your PSU and your motherboard will still have power going through it, that's the ATX standard i'm afraid.
The other thing I noticed was you said your PC was flush against the wall, not good at all, by doing this your preventing air from circulation through you tower, and heat buildup =component failure/overheating is possibly a fire hazard in itself.
Hope this helps,
Jon