The simplest way to mount hard disks into the system case is the direct mounting method, where the disk is screwed directly into a drive
bay. This has largely replaced the use of drive rails, which were common in older
PCs. Drive rails are small metal strips which are screwed onto the drive and then used to
slide the drive into the case. Some people like these, others hate them; they are in fact
still used by some case manufacturers. Some cases also have drive cages, which
are removable brackets into which the drive can be mounted.
Most hard disks used in PCs today are 3.5" form factor
drives, designed of course to go into 3.5" drive bays. Pretty much all newer cases
include these bays. However, there are some older cases that do not have 3.5" drive
bays at all. To allow 3.5" drives to be used in the larger 5.25" drive bays,
mounting kits are available. These are mechanical adapters that screw into the side of the
drive to "widen" it to the size that a 5.25" drive would be, so it can fit
into a 5.25" drive bay.
At one point these mounting kits were often included in retail-boxed hard disks. Today they are much less common, simply because
it's rare to find a PC still in use today that doesn't have a 3.5" drive bay. They
should still be available for purchase separately for a few dollars from stores that sell
PC accessories.
Next: Temperature Limits and Drive Cooling
