If you've been thinking about building a new PC or upgrading an existing one, but the prospect of installing a motherboard seemed too daunting, have no fear. All it takes is patience, a few tools, and a willingness to work inside the cramped quarters of a PC case. Here we'll assume that you're starting with an empty case or that the old motherboard has been removed.
The tools you will need are a Phillips No. 2 screwdriver, forceps or needle-nosed pliers, and a flashlight. An antistatic strap and mat are highly recommended, especially in dry climates; at the least, you will need to be near a light switch or metal lamp to ground yourself frequently. Your workspace should be well lit and have a table big enough to hold the case horizontally. Installation should take about an hour, if you're starting with an empty case.
We'll focus on motherboards that adhere to the ATX specification, though a few new ones may be in BTX format. If you're installing a Micro-ATX motherboard, the process is similar, but with fewer screws.
Set up the case. If you have a tower case, lay it on its side on the table. Remove any panels and internal drive bays—and maybe the power supply—to maximize your work space. Check the location of the motherboard mount points, which are either bumps or hex-head nuts that will accept the mounting screws. Test the screws in the mount holes before you try to install the motherboard.
Install the I/O shield. The I/O shield is a thin aluminum plate—with holes cut for the keyboard, USB connectors, serial ports, and the like—that you need to insert into a corresponding cutout on the rear of the case. (If you forget to do this, you will have to remove and reinstall the motherboard.)
You may have to punch out additional flashing on the I/O shield to make room for optional I/O connections for your particular motherboard. Do this before installing the I/O shield.
Insert the motherboard. Decide if you want to install the processor, CPU cooler, and memory before you install the motherboard. With some small PC cases, it's easier to do it that way; with others, it's easier to add these components later. (Unfortunately, there is so much variation between cases that we can't give specific recommendations.) If you have an aftermarket CPU cooler that requires a bottom plate underneath the motherboard, you'll have to put that in before installing the motherboard.
Get a screwdriver and screw ready, then put one hand on the back of the motherboard (the side closer to the front of the case) and gently apply pressure toward the rear of the case to align the screw holes with the mount points. The first screw you should attach is the center one on the motherboard. Do not screw it all the way in.
Attach wiring. The power connections are pretty simple. Newer desktop motherboards have a primary 24-pin connector and a secondary 4-pin connector to deliver dedicated power to the CPU. Some server or workstation boards may have an 8-pin secondary connector instead of a 4-pin one. Older ATX boards have a 20-pin primary connector and the 4-pin secondary connector.
The front-panel connectors are typically at the rear of the motherboard (nearer the front of the case). These include connectors for the power switch, reset button, power LED, and hard drive LED. They may be color-coded, and are usually in a tight cluster.
Once you've attached all the wiring, you're done. You still have to install the processor, memory, and expansion cards—but those are topics for another time.