I think you missunderstood the meaning of free. I know its rare in our times, but free means you give nothing but recieve something. You know, like free aids!
How did it run smoothly w/o a GPU? ._.
Pics would help.
Make sure your PSU is in the on position, and plugged in. Check all connections. Also check your RAM and GPU seating.
Check your front panel connectors. Also try shorting the two pins that are supposed to be the power button together. If it turns on, then something's wrong with the front panel button, or you just plugged it in wrong.