I recently purchased 2 120mm Fans. I installed one to the front and the other on the side panel. When I turned on my pc it was noticeably slower. Disconnected the fans and it was back to the original speed.
Also, I currently have my fans blowing the air out.. is this right?
No it's not right.
You've created a vacuum in your case.
The fans should be intakes.
Also you'll have better results if they are both front intakes.
The front panel mounts have dust filters.
The side panel doesn't and fans in that location accomplish very little cooling wise.
And alot dust wise.
With the fans mounted in the front as intakes you'll have a configuration like the Antec 300 Illusion.
Adding 2 fans to a 4-pin Molex power output connector from your PSU should NOT have any impact at all on system speed. Are you sure it was affected?
I agree with Davcon - I prefer that fans have intake filters to exclude dust, and that the overall balance provide slightly more intake or air than exhaust fans swo that the case is slightly positive pressure inside. This will ensure that at leakage points the air flows out, not in Incoming air brings dust. I admit that others disagree on that balance argument, but I like my way.
I am guessing the computer slowdown is related to the lack of cool air entering the system thus overheating your computers vital parts. Remember to always balance the airflow with an intake fan and an exhaust fan. There are other options too like the top and side fans providing for extra ventilation.