Computer help: Hardware Conflicts in recently built machine

Sounds like a bad cable

To me, this sounds more like either a bad IDE cable, or the cable isn't fully connected to one or all the sockets. I'd check to make sure the connections are good, and if they are, getting a new IDE cable.

It's incredibly rare to see a hardware conflict these days, now that the ISA bus is long gone. Two devices fighting over a specific IRQ or DMA address was about the only real source of hardware conflicts there ever was. Nowadays, that's all managed by the computer. You can sometimes have driver conflicts, but that too is pretty rare. It just has yet to leave the collective psyche of computer users. You could have two devices jumpered to master, but that wouldn't cause intermittent functioning, it would result in both devices being inoperative. Possibly even preventing the system from booting, but likely only if the devices in question were on the primary controller.