If you wanted to build your own PC, picking the best case used to be simple: Pick the size -- desktop, mini-tower, mid-tower or full tower. Pick the power supply Install your PC

Okay, so it wasn't quite that simple. There were cases that had interiors seemingly made of pot metal, or full of sawtooth edges just waiting to slice open an unsuspecting finger, so you'd avoid those. But beyond a few niceties, there really wasn't a lot of choice. I used the same monstrous In-Win IW-Q500 case for years -- and you can still buy them. But today, things are different. For the most part, PC cases have evolved beyond the beige or white box.

The PC Case Menagerie New case designs and new materials have emerged. These range from all-plastic cases that achieve EMI shielding using a thin layer of metal, or all-aluminum cases that can transfer heat more efficiently. The internal designs have improved, too. Almost all current cases -- even low cost ones -- have rolled or de-burred edges, so there's less chance of spilling blood on your spanking new motherboard. Detachable drive bays and slide-out motherboard trays have become more common, too. It's easier to get cases with semi-custom features, as well, like transparent side panels, enhanced cooling solutions and even airbrush painting.

Motherboard Form Factors: Cases now come in a variety of form factors and sizes, making for greater flexibility in choice and placement. However, you are still mostly restricted to a couple of motherboard form factors. While VIA is busy proselytizing its mini-ITX form factor, and Shuttle makes hay with their mini-cube Flex-ATX motherboards, most motherboards come in the ATX form factor, with a few micro-ATX boards filling in the gaps.

We're going to focus mainly on micro-ATX and ATX solutions in this article. Later, we'll take a look at more compact form factors, as more motherboard solutions emerge.

Needs Assessment Before you buy a case, you need to closely examine your PC usage: Are you building a system primarily for gaming? In that case, you'll need a good power supply and good cooling. Are you building an overclocker's hot rod? Then cooling and a really beefy power supply become paramount. Will this system live in a quiet office environment? Compact size and noise can be major issues. (For more information, see Silencing Your PC.) Will the system be used for any type of professional authoring application? In that case, you'll need lots of drive bays and room for expansion.

Let's take a look at some useful, general case characteristics – we've organized the rest of this story by those sections. . Along the way we'll take a look at some specific examples of cases we've used in the recent past.

As we've seen in our review of the Shuttle SB51G, you can build a high-performance PC in a compact box. Still, this small form factor lacks some flexibility and compromises on the power supply and cooling capability.

Micro-ATX: If you're interested in compact form factors, but you need a little expandability, consider micro-ATX motherboards and cases. Cases like the In-Win IW-L545 (check prices) are less than 14 inches (35.5cm) tall, and can be used as tiny towers or compact desktop PCs. You can get somewhat larger micro-ATX cases, like the Yeong Yang YY-3491 (check prices), which is a shade over 14 inches (35.5cm) tall, but will accommodate a full-size AGP card and a 300W power supply. The depth and width of these cases vary, so check the measurements in all dimensions, especially if you plan on squeezing a PC into a tight space.

Note that micro-ATX motherboards are often limited in expansion capability, usually having three PCI slots. But if you don't need more than three slots, then these compact PC cases can be useful.

Bear in mind, though, that these types of cases are not well suited for the inveterate DIY fiddler (like yours truly). The interior space of these cases can only be described as cramped. You wouldn't want to pop these cases open too often, just because upgrading a motherboard or even memory can be an exercise in patience. But they take up little room, and are a great fit for users who may not be upgrading often.

Mid-Tower: For those of us who are constantly upgrading, the answer lies in either mid- or full-tower cases. "Mid-tower" actually spans a range of case sizes, from about 16 inches tall (40.5cm) to roughly 19 inches tall (48cm). For many power users -- particularly gamers -- the mid-tower is the sweet spot. They offer almost all the features of full-size towers without the bulk. The smaller mid-towers can be somewhat cramped, however, though clever industrial design can mitigate the tight quarters.

Full-Tower: Finally, there are the Hummers of the PC world: full towers. Originally intended for pedestal server applications, full tower cases are popular among the bleeding edge set -- those people who are either constantly opening their cases and swapping out gear, or into serious overclocking, and need the space for water block coolers, extra fans and other accoutrements. Full towers are 20 inches (51cm) tall or higher. If the idea of a full tower case floats your boat, then consider the space the case will live in -- sometimes, you can have too much of a good thing. We once picked up a full tower Addtronics 7896A (check prices), only to discover that it wouldn't fit in the space we had allocated it -- underneath a pretty tall table. At over 26 inches tall (69cm), it borders on the ludicrous for most desktop-style applications. On the other hand, if you need six exposed 5.25 inch bays, then the 7896A or something similar, such as the Chieftec DA-O1W will fit the bill.

Of course, if you need all those drive bays, but don't have space for a tall case, consider a cube-shaped case. The footprint is a bit larger, but a cube, such as the YY-0221 (check prices)might be the ticket. Think of it as a full tower case that's been chopped in half, then the two halves glued together to make a big cube. The motherboard and expansion cards go in one side, while the drives slide into the other half of the case.

Not all full towers are huge. One of our favorite configurations is the Antec SX-835II, (check prices) which is also available as the Chieftec DG-O1W, sans power supply. At about 20.6 inches tall (52cm), it will fit under most desks. The downside is that it's pretty hefty, given the sheet steel construction.

Aluminum, or not, seems to be the main decision.

In theory, sheet steel does a better job of reducing EMI (electromagnetic interference). In practice, most systems are grounded pretty well, and you won't see much interference with consumer electronics devices. Sheet steel cases might be better if you're constantly working inside them. We use Antec SX-830's and 835II's here at ExtremeTech, and have found them to be workhorse cases -- but they weigh about as much as a Clydesdale, or so it seems after a long day. We've experimented with aluminum cases, but we wouldn't use one for day-in and day-out testbed use. Aluminum cases tend to be more fragile, and are easily dented or can be damaged in other ways if you're swapping gear in and out on a daily basis. But aluminum is great for most users who aren't popping open the case several times a day.

However, like steel cases, not all aluminum cases are created equal -- and the price differential between the various aluminum cases are substantial. Whereas a high end steel case might cost $120, a high end aluminum case can run well over $300. Now, that $300 typically buys you a lot of accessories and a fancy paint job. But it's still more than 3 C-bills for a case.

You can also buy cases in various colors. As one wag noted, "black is the new beige", but in fact, cases now come in a variety of hues. You can buy PC cases that are iMac white, black, metallic charcoal, red and blue -- and those are off-the-shelf colors. Sheet steel cases are painted, while aluminum cases may be painted or anodized. Beige has simply become one of many color options.

Form factor is certainly important, but it's more dictated by external concerns -- the space available or desired for the PC. However, if you're a dedicated DIY-er, then you'll be working inside your case often. It's amazing how considerations of the external size vanish the more you work on the inside of the case. Let's examine some key features you should consider.

Rolled Edges: The first one is absolutely essential: rolled or de-burred edges. Most of the cases we've seen lately now are friendlier to your flesh. Gone are the rough edges that look like they were designed to saw through green wood. Still, you do occasionally see an internal edge that's sharp enough to slice a finger. Check out any metal edge that may be exposed while you're working inside.