It should be looking for your hard drive. One of the power supply connections needs to plug into that. Depending on the type of hard drive you have, the connector type will vary. I'd think the first thing you need to do is make sure it's attached properly to everything that needs power from it but I cannot help much in this regard. All drives will need power. The MB will power and it's likely an additional CPU power connector will be needed. The MB connector will be the largest. You can't miss it. It's rectangular and will have 2 rows of either 10 or 12 pins each. The CPU connector attaches to the motherboard and generally has 4 pins on a square connector. IDE hard drives and CD ROM drives use a 4 pin "molex" which will have two black wires, one yellow and one red. SATA drives have their power wiring wrapped in a sheath and aren't individually visible. It sounds like you're ok as far as what goes into the MB or you'd get no BIOS power on self test. I'd be checking the hard drive connections first. You should also be able to interrupt the POST to see if the hard drive has been detected. If it has and listed in the boot order but still shows a boot failure, you have another problem.