You should be able to boot with just the MB, CPU, keyboard, video card and RAM and see the POST (power on self test) bios setup screens. You don't need drivers, HD, CD/DVD, operating system, etc.
If you can not boot to POST then something is assembled wrong or with an older video card you may have fogotten to plug in the second pwoer plug from the power supply to the video card. These require an adapter that is provided with the video card.
Most 5800 cards did require the extra power connector. Newer model cards will still boot and pop up a screen that says you forgot to connect the power cable. Old cards just sat there with a blank screen. Make sure you plug the adapter in the right direction
If the video requires and has a second power cable check how the MB is installed. Make sure the screw heads are centered in the MB holes otherwise the MB can short to the case and it won't boot. Also make sure the video card is fully seated in its slot. Sometimes you have to bend the rear panel plate to make it fit right.
CHeck list in the order they should occur:
Do the power supply and CPU fans spin? -- No, PSU or MB shorted to case
Do the keyboard light flash? -- No, dead CPU or MB
Do any beeps occur? -- No, MB or CPU, older vid card power plug missing
Does POST screen appear? -- No, vid card power, monitor, or vid card.