A fan inside the power supply prevents the parts inside a computer from overheating. To ensure the fan can properly circulate air through the computer, make sure the fan vents on the computer case are not blocked.

An Uninterruptible Power Supply (UPS) protects a computer from blackouts, brownouts and surges. A UPS contains a battery that stores electrical power. If the power is interrupted, the battery can run the computer for a short time so you can save your information.

A power supply changes the alternating current (AC) that comes from an outlet to the direct current (DC) that a computer can use.

A monitor port connects a monitor. You can connect a monitor using an analog or digital connection.

Most people buy a new hard drive to provide more storage space on a computer. Hard drives are roughly doubling in storage capacity every 18 months, which means you can buy a much larger hard drive every few years. Buying a new hard drive is less expensive than buying a new computer.

You can copy old or rarely used files from your computer to an additional, external hard drive. You can then remove the files from your computer to free up storage space. Using an additional hard drive to archive data is useful when archiving a large amount of information.

You can buy an external hard drive to store backup copies of files stored on a computer. Backing up data provides extra copies of files in case the original files are lost or damaged or if you accidentally change or delete files. Using a second hard drive to back up data is useful when you regularly back up a large amount of information.

If your hard drive fails, buying a new hard drive will be less expensive than buying a new computer. Before you buy a new hard drive, you can take your hard drive to a computer specialist to see if they can fix the hard drive or at least recover the data on the drive. If your computer is more than a few years old, consider buying a new computer.