Hard drives failing when DVD drive connected

I need some help here. My PC, which I've recently tried to update by adding a 80gb hard drive to compensate for /t killing my hard drive space, won't work. The usual setup of my PC has been one master, one slave on the Primary IDE, and the DVD burner set to master on the Secondary IDE.

When I try to set the 3rd hard drive as slave, or as master, while changing the DVD burner to master/slave as required, the PC never gets past BIOS as it always fails to detect any one of the hard drives. And now, my PC refuses to work with more than two drives! Does the problem lie with my 350W power supply, motherboard, or the hard drives themselves?

>>3
Utter bilge. Where'd you get that ridiculous idea? I've had anything up to three IDE drives (and a CD/DVD drive) connected to the on-board IDE interface with no problem - you just have to have a PSU that's up to the job, and to make sure your jumpers are set correctly.