Sounds like a possible short in your motherboard. Since items directly connected to the power supply work, and nothing else.
Does the heatsink (fan on your processor) start?
I've had a similar issue, and it was my tuner card and frontside Firewire, AND my floppy drive i had fried some how.... ugh... but atleast the computer was fixable!
Try disconnecting your oyther drives and all unnecessary parts in your mobo... don't forget to leave the power switch plugged in.
The confilict was not likely an issue, but the process of installing the drive may have caused static build up somewhere and upon boot it caused a short and now it will not function while that device is still attatched.
*Simple cases first, before resorting to all out havoc and destruction of your computer (j/k)
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