dude the power plug to your cpu, which actually powers the power supply, and the power connectors inside the box are different. you get 110vac from your wall outlet, it feeds your power supply, and your power supply converts the 110vac to 12vdc, which then feeds your HD. just cut the end of the power plug off that plugs into the cpu and use that for your power source. you could even wire a new plug end into it so that you can plug everything in inside your pc tower.
i think in order to power your lights you need ac power and not dc power. the fans however do run off of dc power, so if you want to run them off of ac power ( household plug ) you need to get a 12v dc adapter.