The components of a PC system are mounted within a chassis or case. The main feature you must first decide on is which form factor the case needs to be. Several somewhat standardized form factors are available for PC chassis, including:

• Slimline Desktop

• Desktop

• Mini-Tower

• Mid-Tower

• Full Tower (Server)

• Large Server

• Rackmount

The Slimline chassis are typically used with NLX form factor boards that are a riser card design. Recently, an addendum to the ATX form factor was created that enables riser cards to be used, allowing ATX boards to be used even in Slimline systems. In addition to the case form factor, the following are several other things you should consider before purchasing your case:

• Motherboard form factor supported. A given chassis usually accepts one or more standard motherboard form factors. Most of the chassis accept ATX (or Micro-ATX or Flex-ATX) form factor motherboards, whereas some accept Baby-AT form factor motherboards as well.

• Motherboard mounting mechanism. Some chassis include removable plates or trays that allow the board to be mounted outside the chassis. This enables the board to be more easily installed and facilitates easier servicing later.

• Power supply form factor supported. Most modern chassis support ATX or SFX form factor power supplies.

• Power supply included or separate. Many include the power supply as standard, but others do not. Usually, I prefer cases in which the supply is separate because that enables me to choose the specific power supply myself.

• Number of 3 1/2'' drive bays (internal and external). Hard drives are typically installed in the internal 3 1/2'' drive bays, whereas floppy, LS-120, Zip, and some tape drives are installed in external 3 1/2'' bays.

• Number of 5 1/4'' drive bays (external). CD and DVD drives as well as some tape drives install in 5 1/4'' drive bays, which are almost always external.

• Number and size of cooling fans supported. Most modern cases have mounting provisions for several additional cooling fans of different sizes. Be sure the case you choose has sufficient fan mounting provisions to provide the cooling your system will require.

• Ease of disassembly (tool-free or not). Some cases are easily disassembled without the use of tools, whereas others require simple hand tools.

• Front panel USB supported. Many newer cases feature front-mounted USB connectors, which are a major convenience.

These are just some of the criteria you should use when selecting the case for your next system.

Custom Cases

Sometimes the standard cases don't fit the bill; in those situations you might want to investigate using a more specialized or custom case. Several companies make specialized cases for unique systems. These cases offer features such as multiple drive bays, unique appearances, and specialized cooling.

Perhaps the most unique cases on the market are those by Koolance or Chip-Con. These companies market cases with built-in refrigeration units in the base, which are connected directly to a thermal plate that mounts on the CPU. The plate runs at temperatures as low as –40°F (–40°C) and can maintain a CPU temperature in the –18°F (–28°C) range with processors generating up to 150W.

These cases also feature an LCD temperature display on the front for monitoring the temperature, and a safety system shutdown is designed to trip if the processor overheats. They have models available for Socket A through Socket 478 processors. The only drawback to these cases is the expense; they cost about $500–$600 each.

They also do not include a power supply, which would cost another $100–$200 for something 300W or greater to go with it. Another company offering special cases is PC Power and Cooling. It offers a line of heavy-duty, solid steel cases with multiple drive bays for serious expansion and server use.

For those who want something that's different and sure to evoke stares from all who see it, PC Power and Cooling also offers a tower case with a chrome-plated front bezel and black cover.