ATX Lab Power Supply Help.

[Prospero]

Hi,
I recently converted an ATX PC power supply to a lab supply. I connected -12V, +12V, 3.3V, 5V and Ground to binding posts.
I added 2 LEDs to the Gray and Purple wires and connected a 750ohm resistor between the LEDs and ground.
Then I put 2 10w 10ohm resistors in series between +5V and Ground.
Finally, I added a switch between The Green wire and Ground.

It all worked fine the first time, then when I flicked the switch connecting the Green wire to Ground off and on again it just caused the fan to twitch. One of the LEDs was lit, but the power supply was in standby. So I plugged it out and in again, it worked fine flicked the switch on and off again and the same problem, after plugging it out and in again the problem still continued.

So, when I plug it into the mains one of the LEDs turn on but when I turn on the switch the fan inside twitches. I have tried bypassing the switch by connecting the Green wire to Ground but I still have the same problem.

Any solutions?