If you follow ALL the wiring from the front of the case, you should see a Molex (the same power conn. used for CD/DVD drives) Just unplug that.
That is how it worked on my Antec Sonata II, and I purposefully didn't plug it in during my build. But with people always kicking my ninja-black case in the dark when gaming and watching movies, I figured it was SO DAMN bright that it was a good insurance they'd spot it.
Also, sometimes I have it running so quiet I forget to turn it off before heading off to bed, so these are just some good points to consider.
I HATE when my computer gets KICKED !!!!