Hard drive on the fritz? Maybe your computer's monitor is flashing incomprehensible error messages at you. Maybe it makes you feel like you want to throttle the person who first used the term "user-friendly" and the word "computer" in the same sentence.

Your computer's acting up - again - and you think it might be time to call an expert to repair it. But how do you know who to turn to, when just about anybody can open up a computer shop and say they can fix your machine? CBC News Marketplace recently discovered that some of those rent-a-geeks you can hire may wind up costing you more than you bargained for.

For most of us, the mysteries behind what makes a computer work are on par with what's under the hood of our cars. We want to be able to count on both without worrying about what makes them tick.

But there are simple car maintenance tasks that just about everyone knows how to do, such as filling up the windshield washer fluid container without confusing it with the brake fluid.

And so it can be with computers.

There are steps you can take that can help you keep your computer running happily, and also avoid hefty bills and heartache if something goes wrong.

Get to know your computer

Your monitor is not your computer. It only displays what the central processing unit — the box that contains the heart, soul and brains of your computer — tells it to. Your monitor must be connected to the CPU in order to get those messages.

Your system will also probably include other peripheral devices, like a modem that connects you to the internet, a printer and perhaps an external hard drive, where you can back up data.

Do not throw away the manuals that come with your system. You just might need them one day.

Run anti-virus software

Nothing ruins your day like a file-chomping virus, to say nothing of Trojan programs that allow hackers to take control of your machine or steal your personal information. Up-to-date anti-virus software will take care of most viruses and Trojans.

Run a spyware scan

Spyware is a program that is installed on your computer without your knowledge or consent. You can get them simply by visiting certain websites. These programs can collect information about your computer use. They can also direct your web browser to certain sites.

Run a spyware scan regularly to clean junk files from the computer. Most antivirus packages now come with spyware removal tools, and there are also free or low-cost packages available online from sites such as download.com.

Empty the Recycle Bin or Trash folder on your computer

Old files build up here, take up space and can slow down your system.

Clear the cache on your web browser

The cache is a record of the web pages you've visited, and it can clutter your hard drive in a hurry. In Microsoft's Internet Explorer, for example, click on "Tools" in the menu bar at the top of the page; then choose "Internet Options"; then click on "Delete Files". (Tip: while you're at it, you can also click "Delete Cookies", although this will also clean out cookies automatically. Remember login information for subscription sites you visit regularly).

Clean up your e-mail program

Clear out unneeded files from the "Deleted" and "Sent" folders of your e-mail program — that is, if you use a dedicated e-mail program. If you access your e-mail online, this doesn't apply. But for e-mail programs that are installed on your computer and store files on your PC's hard drive, all those old messages and attachments eat up disk space.

Degfragment your hard drive once a month

This will speed up your system and reduce some wear-and-tear on the drive. In "Windows", go to the "Start" button, then "Programs", then "Accessories", then "System Tools" where you'll find the program "Disk Defragmenter." Run it. (Tip: When you find the "Disk Defragmenter" program icon, right-click on it; choose "Send To", and then click "Desktop" – "Create Shortcut". This will put an icon for the program on your main Windows desktop, so that it's easy to find the next time you want to run the program.)

Vacuum the inside of the computer

Dust is your enemy. After vacuuming, use a cotton swab to clean the blades of any dust-laden fans at least once a year.

Dust causes two problems: it clogs fans, reducing airflow (and in some cases even causing the fan motor to jam) and it acts as an insulator, preventing computer components from shedding excess heat. That heat is the enemy of electronics — when computers get too hot they can start to generate errors. As well, the life of the components is also reduced.

Even novices should be able to handle the cleaning job. First, touch the side of the computer's metal case to pull any static electricity out of your body (a static shock from your finger can ruin a chip). Then turn off and unplug the computer to prevent the chance of electric shock. Using the vacuum's smallest attachment, suck out the dust bunnies. Just be gentle around the electronic components, and be careful not to dislodge any cables (particularly SATA drive cables — see the note below).

Don't scrimp on your power bar

Connect your computer to a good-quality power bar or uninterruptible power supply (UPS). Cheap power bars don't clamp down on an electric jolt quickly enough, so juice can get through in a lightning strike or power surge and damage your computer — invest an extra $20 or so in a good one (the better ones tend to come with a guarantee to replace any electrical equipment that gets fried while attached to the power bar).

The benefit of a UPS is that it has a battery and can protect against surges, failures and brownouts (ie. when power drops suddenly, something that can cause computer hiccups or damage). The UPS monitors the flow of power, regulates it if there's a surge, tops it up from the battery if there's a brownout, and also gives you several minutes of battery power to save your work and shut down the computer safely if the power fails completely.

Back up your data

Regularly. At least once a month. Few people do it, yet every single person who encounters a data-corrupting disaster wishes they had. Computer drives can be damaged by a virus, a software installation problem, or something as simple as not shutting the PC down properly.

Hard drives also have moving parts that will fail eventually. Reconstructing a stricken hard drive can cost hundreds or even thousands of dollars, and there's no guarantee you'll get everything back. For less than $100 you can buy an external USB hard drive and use it to quickly back up things like your digital photos, music, documents and financial records — you can copy gigabytes worth of information in a matter of a couple of minutes. Some drives come with backup software to automate the process.

Alternatively, use recordable CD or DVD discs to back up important files. In either case, a good idea is to keep the external backup drive or backup discs in a fireproof/waterproof box just in case (you can get them at most hardware or department stores).

If prevention fails

Prevention didn't do it? Here are some simple steps you can take if you're having a computer problem but before you call in someone to repair your machine.

Find a friendly geek

For simple problems, a family member, friend or neighbour who knows a bit about computers and can spot simple problems can save you a costly service call.

Check the internet — if you still have a connection

If you can still access the internet, there are a lot of resources you can rely on to help troubleshoot your problem. If your computer is displaying error messages during the booting up process, make a note of what those messages say. Type them into a search engine. You should be able to find a host of forums, message boards and other sites where people with similar problems have posted fixes.

Also, the manufacturer of your operating system will have extensive help information on their site, assuming your operating system is still supported.

Make sure all the cables are connected

It's amazing how many computer problems involve a simple loose connection. This includes power cables from the wall socket to your computer and monitor, as well as the cables going into the back of the computer from your monitor, mouse, keyboard, and internet connection (phone or cable). Cables that trail under a desk often get kicked loose from their sockets, or can work loose from the back of the computer. Also, plug a lamp into the wall socket that your computer uses to make sure you haven't simply tripped a breaker on your home's electrical panel.

And if you have speakers, make sure they, too, are connected to the computer.

Advanced tips

If you're running Windows XP or Vista and your computer will boot up when you turn it on, go to the "Start" button, choose "Help & Support", and click on "Undo changes to your computer with System Restore." Follow the instructions, and this could help you unravel simple software problems, such as a corrupt configuration file or a glitch caused by a newly installed program or patch.

Sometimes re-installing the operating system will also clear out problems associated with bad files.

If you're comfortable looking under the hood, an easy thing to check is the drive cables. Before you go in, touch the side of the computer's metal case to pull any static electricity out of your body (a static shock from your finger can ruin a chip). Then turn off and unplug the computer to prevent the chance of electric shock. Remove the side or top panel, and look at the back of the hard drives and optical drives. Each drive should have a power cable and a data cable plugged into it. The other end of each data cable plugs into a socket on the motherboard. The data cables for Serial ATA or SATA drives in particular have a tendency to work loose (the cables are usually red with black connectors at each end).

Still no luck?

Well, it may be time to call in a professional. Before taking a stroll through a phone directory and picking out a name at random and wondering what their qualifications really are, ask a friend if they can recommend someone.

You probably wouldn't walk into any garage, hand over your keys and ask the mechanic to fix your car. And you probably also realize that if you go to a large car repair chain, the mechanics also double as salespeople, looking to boost the bottom line.

The same goes for the folks who work for computer sales and repair chains. You may one day need them, but if you go in having done your homework, you might be able to keep your bill from soaring too high.