PC cases come in all shapes and sizes. The purpose of a PC case is universal in that all cases are meant to hold your PC's innards. That is no big surprise, but there is more to a case than you might think. There are essentially two classes of cases, mass-market cases (usually boring) and after-market cases (more theatrical).

If you have a mass-market PC, you will have a very generic case that basically holds your PC. Most of the time these cases are embossed with the logo of the manufacturer, but don't really have any other distinguishing characteristics. The after-market or specialty cases are more involved and usually have many unique features. Anything from internal and external lightning to decorative inlays and artistic paint jobs, and everything in between. There are several types of cases, having to do with the type of motherboard it was meant to hold. Some are made from steel, aluminum, plastic, plexiglass, and other materials. Some are compact, while others are monsterous and meant to be displayed as a piece of conversation-starting art. Let's take a look at some of the wild and wooly offerings available for dressing up your PC.

Just for fun, here are a few of the latest top selling cases from TigerDirect.com. These are all different prices, compositions, and types, to give you an overview of what cases exist:

Name Tempest Material Steel & Plastic MFR NZXT Motherboards ATX, Micro ATX, Extended ATX Price $99.99 w/ Power Supply? None Form Factor ATX Mid-Tower Model TEM-001BK Dimensions 22"d x 18"w x 20"h

Name M923 Material Steel MFR Ultra Motherboards ATX, Micro ATX, Extended ATX Price $89.98 w/ Power Supply? None Form Factor ATX Full-Tower Model ULT40125 Dimensions 20"d x 8"w x 21"h

Name M998 Material Aluminum MFR Ultra Motherboards ATX, Micro ATX, Extended ATX Price $139.99 w/ Power Supply? None Form Factor ATX Mid-Tower Model ULT40069 Dimensions 20"d x 9"w x 18"h

Name Spedo Material SECC MFR Thermaltake Motherboards ATX, Micro ATX                         Price $224.99 w/ Power Supply? None Form Factor Full-Tower Model VI90001W2Z Dimensions 20"d x 9"w x 18"h

Almost all PC cases have a USB front panel so you can connect digital cameras and other devices to easy-to-reach ports on the front of your PC. This has become standard in the last few years, and some are hidden behind a panel you access by pushing the edge or sliding it out of the way to reach the ports. This is one innovation of late that has been helpful to allow PC owners to not go under-desk diving to find a port several times a day. Older PCs won't have this feature, and it is tough to retrofit it, since this is a feature not only of the case itself, but requires a corresponding controller chip and connector on the motherboard.

The internal layout of nearly all cases is designed to maximize airflow and help keep your PC components cool enough to operate for extended periods of time. Some configurations are better conceived than others, and it seems that more often than not the case designs don't help airflow enough, and tends to get in the way of good ventilation. This can cause overheating, premature component failure, and all sorts of other issues. Dust generally gets more trapped in the case too if the airflow isn't well-designed. Too much dust, not enough air, and running a PC 24/7 can cause fans to fail as well. Most cases have one fan in the rear that sucks air out of the case, helping the heated air leave the case and help cool the heat generating parts, especially the processor. Cooling is one area of computing that the custom enthusiast cases take more seriously, since many of the cases are made to house gaming guts or some other high-end graphics setup. Cooling become vitally important for these PC hot-rods because the processor gets much hotter than in regular PCs, and heat will fry things if not properly handled in extreme pressure and high-speed situations.

There comes a point when air cooling isn't adequate to keep things chilly. This can sometimes be the case right out of the box for mass-market PCs, especially if your PC is on the floor, on carpet, under a desk, etc. This will severely limit the cooling capability of your machine. Most of the time, simply putting the PC in a bit more open air will aleviate the problem, such as next to the desk, a few inches from the wall, instead of under it. If you do it right, you can get the heat from the fan to point right at your feet to keep them warm in the winter. That is green computing — reusing that energy to heat your feet — brilliant! Someone call that patent place... Alternatives to air cooling have been tried for at least a decade now, and some are more successful than others, which are nothing if not nostalgic.

Some slightly too geeky company produced the refrigerator PC — as I liked to call it — which basically turns your PC into a mini-fridge, although not the kind you can put your soda in next to your pool table (unless your case is huge). This method of cooling is so effective that you can rachet your computer's speed up (the custom-built PCs that is) way past its regular parameters to get awesome performance out of it, because this fridge system would cool it to below zero. The fridge system is cool (as in cold) and cool (as in awesome, rad, far out, etc.) but not very economical. It costs too much to run for most PC buyers, has other issues, and requires another six to eight inches under your PC for the fridge unit to sit, causing space issues too. It never reached the mainstream but is still a unique and viable idea. We may be seeing it make a modernized return to the limelight soon, so keep an eye out.

Another method, much more widely used in enthusiast PCs is the liquid or water cooled PC. This uses the same idea as your car to keep cool. You essentially have a water filled tube running through your PC that is attached to the processor block, since that is the main culprit in high heat situations. There are all kinds of accessories that go with a liquid cooled setup to make it more efficient and even lit up and colorful. Some enthusiasts even put fish in a protected portion of the case, as a sort of inside joke on water cooling. The downside with this method is you have to be very careful not to let the liquid or water escape the tube and ruin your high dollar equipment it was meant to protect. With the right gloves, tools, sci-fi re-runs and snacks it can be done carefully and work very well. It is not recommended for generic PCs, and generally isn't needed either. 

The newest method of cooling just now hitting the market is the oil-filled PC. In this case, the manufacturer will use an airtight container as the PC case, remove the fans and other air-flow cooling components, ducts and heatsinks, etc. and fills the case up with non-conducting dielectric fluid, usually oil, but it can also be a synthetic made for the express purpose of PC cooling. All PC components are immersed in the oil, making the PC completely lubricated 24/7 and completely cool. The fans gone, it also makes PCs near silent in some setups, and from all accounts it seems to work well. Here is a demo so you can see for yourself: 

Cooling isn't the only thing that makes a case special, but that is a lot of what a case needs to do for you. You can get lights, fans, custom hardware, paint, and all sorts of personalization products to make even your mass-market machine into a one-of-a-kind if you so choose. Case-modding as a hobby has nearly become a sport, so check it out if it sounds interesting to you. Cases are hardly the most interesting part of your PC, but they are important to the well being of your computer just the same. Photo: TigerDirect and Xion

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• Peripheral Connections 101: USB and Bluetooth standards
• Solid state drives 101: Why should you care?
• Virtualization 101: How to run multiple OSes at the same time
• Multiple monitors 101: Why you want them, and how to set them up