New computers are expensive, even the entry-level ones, which prevents many people from owning a computer. With so much of normal life revolving around computers the need for access to a computer increases every day. Want to buy a book? You will need a computer because all the book stores are closing. Want to take night classes? Many are only offered online. Want discounts on your monthly bills? Many companies offer discounts if you opt to receive an electronic bill instead of a paper bill.One solution is to use the free computers available at public libraries. This is great service if you need to use them and are available to use them during library business hours. Borrowing a computer from family and friends is another option but that gets old in hurry.Another solution is buying a used computer. The average computer user does not need a high-end computer with the latest and fastest processor so a few year old computer is more than adequate. Fortunately for these people there is no shortage of people looking to sell computers that are in great condition and only a few years old.Many people get a new computer every couple years either because they just want the latest and greatest technology or because they need to processing power for graphics design or engineering applications. These are the ideal people to buy a used computer from because there is a good chance that when they bought the computer a couple years ago it was the top of the line model with the fastest processor available. A computer purchased a couple years ago with the fastest processor available at the time becomes obsolete a lot slower for the average user.There are relatively few components in a computer that are prone to failure which makes the due diligence process before buying a used computer fairly simple. A few simple tests and thorough inspection are sufficient in most instances and do not require a computer technician and can be performed by persons with basic knowledge of computers.Hard driveA computer’s hard drive is vital to its operation and its failure can mean more than just a non functioning computer. It can also mean loss of data stored on it. Backing up important files is good practice for any computer user but especially someone buying a used computer. Affordable back up options include burning files to DVD if the computer has a DVD burner and USB thumb drives.Hard drives are one of only a couple computer components with moving parts so they can wear out. A hard drive that makes excessive noise or a noise whose volume or pitch varies is not a good thing. The best time to listen to a hard drive is while it is reading or writing data such as while the computer is booting up.Cooling fanSeveral components in a computer and on a mother board generate significant heat so computers have fans to keep them cool. If computer’s fan is not working there is a good chance that some damage has been done to its components. Excessive dust and dirt on the cooling fins of a CPU can prevent the CPU from cooling properly thus increasing the likelihood the CPU may be damaged. To determine if a fan is in good condition listen for an even, low-pitched hum.Operating systemReboot a computer several times to test the operating system. It should not take an overly long time to boot up and it should not hang up or pause during the boot process.AccessoriesAll other hardware should also be checked. This includes things like CD or DVD drives, the drawers should open and close smoothing and you should be able to read data from a disc and if they are writable drives you should be able to write to a disc. The keyboard, monitor and mouse should be inspected as well.