Several types of diagnostic software are available for PCs. Some diagnostic functions are integrated into the PC hardware or into peripheral devices, such as expansion cards, whereas others take the form of operating system utilities or separate software products.

This software, some of which is included with the system when purchased, assists users in identifying many problems that can occur with a computer's components. In many cases, these programs can do most of the work in determining which PC component is defective or malfunctioning. The types of diagnostic software are as follows:

• POST. The power on self test operates whenever any PC is powered up (switched on). These routines are contained within the motherboard ROM as well as ROMs on expansion cards.

• Manufacturer supplied diagnostics software. Many of the larger manufacturers—especially high-end, name-brand manufacturers such as IBM, Hewlett-Packard, Dell, and others—make special diagnostics software expressly designed for their systems.

This manufacturer-specific software normally consists of a suite of tests that thoroughly examines the system. In some cases, these utilities are included with the system, or you can download these diagnostics from the manufacturer's online services at no charge; otherwise, you might have to purchase them.

Many vendors include a limited version of one of the aftermarket packages that has been customized for use with their systems. In some older IBM and Compaq systems, the diagnostic software is installed on a special partition on the hard drive and can be accessed during startup. This was a convenient way for those system manufacturers to ensure that users always had diagnostics available.

• Peripheral diagnostics software. Many hardware devices ship with specialized diagnostics software designed to test their particular functions. Adaptec SCSI host adapters, for example, include diagnostic functions in the card's ROM BIOS that you can access with a keystroke (Ctrl+A) at boot time.

Sound cards normally include a diagnostic program on a disk along with the drivers, which test and verify all the card's functions. Network adapters usually include a diagnostic specific to that adapter on a disk, also normally with the drivers. Other devices or adapters also might provide a diagnostic program or disk, usually included with the drivers for the device.

• Operating system diagnostics software. Operating systems, such as Windows 9x/Me and Windows NT/2000/XP, include a variety of diagnostic software utilities designed to identify and monitor the performance of various components in the computer.

• Aftermarket diagnostics software. A number of manufacturers make general-purpose diagnostics software for PCs. This type of software is often bundled with other system maintenance and repair utilities to form a general PC software toolkit.