Hello,
Could your problem possibly be that the power supply isn't plugged in to the motherboard connectors all the way? And when your computer makes the clicking sound, is that all that happens? Does any error message come up on your monitor? You know how many clicks it makes?
I know that when I was taking apart a 486 and was putting it back together, I heard clicks, but the computer didn't boot up, and no error message showed up on the screen. The problem was a Socket-type CPU not being put into the ZIF socket the correct way. But when the CPU was re-inserted correctly, the computer booted up fine.
One thing you could do is experiment with the cable connections from your motherboard to your hard drives. But if there's no error message displayed on your screen, I don't think bad hard drive connections are the problem. Isn't an error message displayed when hard drives aren't connected properly?
Hope this helps, and I hope your computer gets working soon.
Take care,
Mr.C