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How to build a PC

A step-by-step guide to enthusiast system assembly

The best thing about being a PC enthusiast—beyond, of course, the never ending joy of serving as the personal support technician for friends and family—is being able to assemble a system from the ground up with the perfect mix of components for a given budget. That mix of components will vary depending on your needs, but with today's market so rich with high-performance hardware at affordable prices, it's easy to spec a custom system that will blow the doors off pre-built boxes from major PC vendors.

For those who lack the expertise to pick the best available components, we compile regular system guides outlining our recommendations at various price points. These guides are a great starting point for seasoned PC hobbyists contemplating a new build, but they're an invaluable resource for less savvy users seeking guidance as they step into the enthusiast realm.

Users new to building systems from scratch need more than just a shopping list, though. There's an art to assembling a rig from bare components. Building a PC can be a daunting task for a newbie who has never put a system together before. For those folks, we've crafted a step-by-step guide covering the basics of system assembly. Keep reading as we show you how to build a PC from scratch.

Getting started
Before diving into assembly, you'll want to gather a few supplies and find a large, clean work area that preferably isn't teeming with static electricity. As far as tools are concerned, you shouldn't need more than a Philips head screwdriver; one that holds screws in place with a magnetic tip is ideal. We'll also be using rubbing alcohol, Q-Tips, and zip ties. Everything else that you need should be included with the various components you've gathered to put into the system. Yes, you'll need those components, too.

Prior to removing any of the components from their packaging, you'll want to take the precaution of grounding yourself by touching a large, metal object like a table base, filing cabinet, or your PC's case—whatever's nearby—in order to discharge any static electricity you may be carrying with you. Static electricity can be harmful to PC components. Some folks prefer to use an anti-static wristband in order to keep themselves grounded.

Assembling the core
The CPU lies at the core of the modern PC, making it an appropriate place to start our build. For this first step, you'll of course want the processor, and also your system-to-be's motherboard.

This particular assembly guide features an Intel processor with a LGA775 socket, so certain steps won't be applicable to systems using AMD processors based on Socket AM2. Socket AM2 isn't hard to figure out, though; processor installation instructions typically come bundled with both the processor and the motherboard.

After laying the motherboard out on a clean work surface, remove the plastic cover that shields the LGA775 socket's pins from harm. Be careful not to bend or otherwise disturb these pins—they need to line up just right with contact points on the base of the CPU.

With the plastic guard removed, you'll easily be able to unclip the lever that holds the socket's CPU retention mechanism in place. Flip this retention bracket back on its hinges to expose the socket in full.

Modern CPUs are keyed to ensure that they can only be inserted into a socket one way, just like a puzzle piece, so you should have no problem dropping your processor into the socket. LGA775 processors, for example, have little indents along opposing edges that line up with protrusions in the socket. If your CPU struggles to slide smoothly into the socket, chances are you've got it oriented the wrong way.

Once the processor is sitting comfortably in the socket, flip the retention bracket back down and use the lever to clamp it into place. This secures the CPU to the motherboard.

With the processor installed, we can move onto the application of thermal compound. Some folks like to apply thermal paste before dropping the processor into the motherboard, but I find that tends to be a little messier without making things any easier.

Before slathering thermal compound all over our processor's exposed cap, it helps to make sure that cap is nice and clean. Gently brush the cap with a Q-Tip dipped in rubbing alcohol to rid it of any dust or oils that it may have picked up from your grubby carefully manicured fingers during the installation process.

Next, we apply thermal compound. Most retail processors that come packaged with coolers will already have thermal compound applied to the base of the heatsink. If yours does, you can skip this step and proceed directly to heatsink installation. However, we recommend applying thermal compound yourself. Thermal compound works best as a very thin layer between the CPU and heatsink, and most heatsinks that come with paste pre-applied use a thicker layer than is optimal.

You really only need a small dab of thermal compound to ensure complete coverage for the CPU. The dollop pictured above is more than enough, and it's best squeezed onto the center of the processor's metal cap.

Next, spread the thermal compound over the processor, ensuring complete and even coverage. Some thermal compounds come with plastic spreaders, but you can also use a credit card or even a finger wrapped in a plastic bag. What you want to end up with here is a relatively smooth layer that's just thick enough to completely cover the processor.

Don't worry about getting a little paste on the CPU retention bracket; it won't do any harm there. You will want to clean up any compound that makes its way onto the motherboard or its surface-mounted components, though. A Q-Tip dipped in rubbing alcohol should do the trick.

Once the processor is glazed with compound, we can turn our attention to the heatsink. If you've elected to do your own thermal compound application, you'll want to make sure that the heatsink's base is scrubbed clean. Rubbing alcohol usually gets the job done, but some heatsinks are slathered with particularly gooey, clingy, or otherwise uncooperative thermal interface materials. It may be necessary to break out more noxious substances, such as nail polish remover, to restore the base of the heatsink to a bare metal shine.

Be careful not to mar the base of the heatsink when removing any thermal compound that may cover it. Some heatsinks need to be scraped clean of thermal compound, and it's best to scrape with something plastic rather than a metal tool that will gouge the heatsink's surface.

With our system's processor blanketed by a thin veil of thermal compound and our heatsink's base scrubbed clean, it's time to mate the two together. Before dropping the heatsink into place, ensure that all four of the heatsink's plastic retention posts are rotated clockwise into their installation position. Next, place the heatsink on top of the CPU, lining up the four retention posts with corresponding holes in the motherboard.

When the posts are lined up, depress the black plastic tabs one by one to lock the heatsink into place. You should hear an audible click as each post locks into place.

Since the area around a modern motherboard's CPU socket is often crowded with tall capacitors, heatsinks, and elaborate heatpipe arrays, I find it's best to depress the retention post that's least accessible first. The post directly opposite that one should be next, followed by the remaining two in whichever order you desire.

After locking the heatsink into place, plug its fan into the appropriate header on the motherboard. The CPU fan header is usually right next to the socket, but if you can't find it, your motherboard manual should have a map highlighting its location.

Note whether the heatsink you're using features a fan with a three- or four-pin header. That information will come in handy when we jump into the BIOS to configure fan speed control, since some motherboards can't auto-detect fan types.