How To Build A PC: From Component Selection To Installation

A great many of the folks who land on Tom's Hardware are already deeply passionate about technology and PC hardware. But we know that others are looking to learn more. We're an inclusive bunch. So if you've never built your own PC, fear not. Our editorial team does it all of the time, and we're happy to walk you through the steps, starting with picking the right parts.

There's a good chance that, even if you haven't gotten your hands dirty inside of a case, you still have a basic knowledge of the components that go inside. Experienced builders often have their ideal configuration in mind before they choose a case. But even a seasoned pro needs to be sure that everything's going to fit inside the right chassis. And of course, enclosures vary depending on what you want to do with your PC. Home theater systems, all-in-ones, flashy gaming boxes, and business-oriented workstations all have their own requirements.

Traditional cases follow the size categories below. However, more modern designs tend to stray from those well-defined standards in the name of differentiation. Mid-tower designs, for example, are now found in nearly full-tower scale. To make matters more confusing, they can even be referred to as full towers, even if they lack the drive bays inside that used to define the form factor.

Traditional Case Sizes
TypeFull TowerMid TowerMini TowerMini CubeDesktop
Height21-24 inches17-19 inches12-14 inches7-9 inches3-7 inches
Width6-8 inches6-8 inches6-8 inches8-9 inches14-17 inches
5.25" bays4-93-61-21-21-3
3.5" internal bays6-122-61-21-22-4
Motherboard Form FactorATX, EATXATXmicroATXmini-ITXATX, microATX
Card slotsSevenSevenFourTwo2-7
Power supplyPS/2 or largerPS/2PS/2 or SFXSFX or TFXVarious

Full towers were traditionally tall enough to hold two power supplies, though many had a second hard drive rack where you might expect to find the top power supply. The interior space of a full-tower chassis is useful in some configurations; however, most mainstream users (and even most enthusiasts) simply don't have enough hardware to fill it.

A better justification for picking a full tower is that the top bays are easier to reach when the case is sitting on your floor. A modern example of the traditional full tower, Rosewill’s Blackhawk Ultra, is the right-most case in the image below.

ATX mid-towers are usually capable of holding full-sized motherboards, full-sized power supplies, several full-sized optical drives (DVD and Blu-ray burners), and multiple hard drives. Well-designed units like the Cooler Master Storm Enforcer (above-left) are well-suited for gaming and video enthusiasts, simply because they support a greater number of expansion cards and hard drives than smaller units. A comparison of our current case reviews to models from ten years ago show that good ideas stand the test of time.

A majority of cases give you room for seven expansion slots around back. Typically, that's enough for a couple of graphics cards, add-in sound, and even back-panel brackets exposing USB or eSATA connectivity. But let's say you love your games, and you're dead-set on building a system with three or even four graphics cards. Specifically seeking out an ATX case with eight or more expansion slots might be necessary, since high-performance cards have thick cooling solutions that use the case’s slot hole for support and ventilation.

MicroATX mini-towers are nearly as versatile as mid-towers in applications ranging from office workhorses to high-end liquid-cooled SLI-powered gaming monsters because of their less-imposing profile and easier trasportability. Mini-towers typically support one or two optical drives and one or two hard drives, and the microATX form factor supports a maximum of four expansion slots. All of those limitations are acceptable for most users.

Mini-ITX cubes typically support a single expansion cards and only the smallest power supplies, though the slightly-oversized Lian Li PC-Q08 above (center) supports larger parts. Relying mostly on integrated features and capabilities, these space-saving enclosures were once only good as office- and productivity-oriented platforms. Now, thanks to more efficient host and graphics processors, we also have access to ultra-compact gaming machines and home theater consoles. Though you'll commonly see these referred to as “small form factor”, the term form factor is better applied to the mini-ITX motherboard found inside. Variations of the cube aesthetic alternatively support ATX and microATX form factors.

Formerly used to raise small CRT monitors up to eye level on flat desks, today’s horizontal desktop cases are mostly restyled for home theater systems. They range from the gaming-themed mini-ITX Raven RVZ01 (pictured bottom-center, above) to the eight-inch-tall full-ATX pedestals laying on their sides. Many of the slimmer models use special half-height expansion cards, though the model pictured above uses a right-angle adapter (called a riser card) to situate a full-sized graphics card sideways. If expansion is important to you, beware of models that use a custom-sized power supply, as those may not be upgradeable.

Want something smaller? The yellow box above is the most compact unit we’ve tested to truly qualify as a performance-oriented machine. Called the Brix Pro, it holds two notebook-sized memory modules, an on-board mSATA SSD, and a 2.5” notebook drive. Shorter single-drive units are available with similarly scaled-down performance, and Intel even jumped on the tiny bandwagon with its similar-appearing NUC (Next Unit [of] Computing) form factor. Most of these machines are available either as a barebones system (no drives or memory) or a complete PC, and all of them use external, notebook-style power adapters.