Cable connections
Here comes the tricky section: getting all of your cables properly installed. There are several cases which can easily be reversed and cause the connection to malfunction, so be sure to pay careful attention.

Interface Cables
First off, let's install the floppy cable, since it's the hardest area of the computer to get to. Most floppy cables today are labeled, so it's hard to plug the wrong end into the motherboard. But as a general reference, the twist that is present in every floppy cable should be closer to the floppy drive than to the motherboard. After that is installed, connect the floppy power connector. It is the small, “mini-molex” 4 pin connector. It's keyed so that it will only work in one direction, so there's no risk of upside-down installation. If your floppy drive doesn't register in that POST screen (more on that later), then pull out the cable on the floppy drive end and flip it.

Now connect the IDE cable that goes to your CD burner. Generally, with the emergence of SATA, only IDE cable you'll be using is for the CD/DVD burner, so just set the jumper on the drive to cable select (CS) so you don't have to worry about it. Next is the power connector for the CD drive. It takes a standard 4-pin molex plug, which should be very easy to find on your power supply's nest of cables.

Now it's time to connect the SATA hard drives. This is probably the easiest cable to connect. Just line up the slim SATA cables so it fits the slot's keying, and connect. It's generally best to use the SATA slots on your motherboard in order (I.E., use slots 1 and 2 before 3 and 4). Most modern power supplies will have an independent cord with several SATA power plugs. Connect these now.

Power Connectors
Find the 20 or 24 pin ATX main power plug as well as the 4 (or in some cases, 8 pin) ATX12V plug, and insert them into the motherboard. They have tabs and retention clips on only one side of the plugs to avoid a backwards insertion of some sort. Once this has been completed, connect the power on, power LED, and HDD LED plugs onto your motherboard. Unfortunately, these pins are different on every motherboard, but they are also clearly labeled, so just follow what it says.

During this time, you should also set up your pci-express power connector, if your PSU doesn't come with one already. Find two independent molex power plugs (I.E., >not on the same cord coming from the PSU) and connect them both to the 6 pin pci-express adapter that should have come with your video card. One final, optional thing you can do is plug your front USB ports into one of the many 9 pin internal USB plugs found on your motherboard. Also, plug your fans into either a 3 pin plug on the motherboard or onto one of the molex connectors. Don't worry about which molex you plug it in to, the power drawn by fans is insignificant.

Inserting Cards
Though you can do this in any order, I've found that installing the video card last results in the fewest headaches. Start at the bottom PCI slot and work your way up, connecting all the cards you have. A general note about putting cards into pci or pci-e slots is that it will take a bit of pressure to get them in, so don't be afraid to put some force on it to make it snap in to place. Don't worry; you'll know when it's properly connected. Once everything has been seated, attach the 6 pin pci-express power to the video card and you're read for action.

Connect the power, monitor, keyboard, and mouse, and press the power button. If you've followed this guide and haven't gotten anything DOA, you should boot to the POST screen. It's all downhill from there.