Right now all I can suggest you test is as follows....
1 Return your DVD and orig HDD to their org ports... DVD/sata1, HDD/sata4 as you originally stated.
2 Try booting with your new drive attached to all the other available ports, one at a time.
3 Try booting with only your DVD and the NEW HDD attached. Even try loading an OS on it to verify it works.
I find it odd that one of your tests prevented the computer from booting UNTIL you unplugged the power cord to the new drive as well. That really shouldn't keep the computer from booting unless there is a problem with the power cable or the drive. You would think the drive is OK since the BIOS detected it properly, BUT that isn't always the case.
I checked the MB manual concerning the SATA ports and didn't notice anything that jumps out at me.
Even if my suggestions don't help you out, PLEASE post back if you finally get the problem sorted.