Have you tried the opposite, connecting all your hdd / dvd / cd drives / fans again and disconnect the mobo ATX 24-pin / CPU 4-pin connectors then "jump start" the unit by simulating the "power_on" motherboard signal by shunting the "PS_ON" green wire to ground via a paper clip or something - then plugging the unit in and powering the rear switch on... Here is an example of the atx jumper:
You *have* to have at least one hdd or cd/dvd drive connected to act as a "pull-up" load to power the unit on. The drives should spin up and the cd tray should be ejectable and it should stay on. If you have a voltmeter you can test voltages.
If it works the unit is probably ok and I would troubleshoot your board / cpu / gpu / memory at this point. Maybe try a cmos clear, and bare-bones config like cpu / mem / video / keyboard / power-on header only can help isolate the problem.
Do you have a voltmeter? Start checking some of the molex connectors to see if there is any voltage flowing through... it might be a faulty PSU, happens at times. Even OCZ's product quality isin't 100%...