What's wrong with your computer? Has your PC stopped booting, or does your laptop crash after an hour or so every single time you switch it on? Perhaps there's a problem with the power cable, or maybe your mouse isn't working properly -- or worse, you've spilt coffee on the keyboard.

The default option for most people is to get on the phone and call a PC repair shop. Or to contact the vendor for some expensive support. But in the vast majority of cases, you don't need to rely on these services. Just make sure you know what you're about to face before you start fixing it.

These DIY fixes will show you just how straightforward it is to repair your computer or laptop yourself.

1. Computer Won't Boot: Check Your Power Cable

There are many reasons why your computer won't boot. It might be a problem with the operating system, or the hard disk drive. The motherboard might also have an issue.

But if you've checked all of these things already, there is another common issue that many people overlook. Desktop PC power cables -- that connect the computer's power supply unit (PSU) to the mains electric -- can simply fail. Perhaps your cable has been bent, causing one of the internal wires to break. If you're in the U.K., it might be that the fuse has blown.

Either way, many PC issues can be fixed with relative ease by simply switching the power cable.

2. Slow or Hanging Computer

A common problem for laptops and desktop computers is slow performance. This is often blamed on things like a hard disk drive that needs defragging, or a slow processor. And if you're running an older computer (say, 5-10 years old or more) then this can be the case.

But the main reason for a slow computer, especially when the processor (CPU) is a highly rated one, is a lack of RAM. Memory is vital for the smooth running of a computer. The CPU uses memory constantly. While a CPU with a larger onboard cache will improve overall performance considerably, adding sticks of RAM to your computer is the next best solution.

Before you head out and buy some new RAM, make sure you know you're buying the right thing. Memory has evolved over the years, with different configurations and connectors used. Laptop RAM isn't compatible with desktop motherboards, for instance. Check our guide to upgrading your computer's RAM. Do you have some left over? Try one of these RAM recycling tips!

3. Spilled Coffee on Your Laptop? Try This!

Accidentally pouring liquid over your keyboard is a common occurrence, especially in offices around the world at 8am. Hot or cold, liquid with a heavy water content doesn't mix with electronics. If you're using a desktop computer, it's a relatively trivial matter to attach a new keyboard and carry on working.

But what if you spilled coffee on your laptop keyboard?

Under the keyboard of your laptop are the workings of the computer. The processor, RAM, motherboard, storage, and the battery! None of this is watertight. So how do you repair your laptop?

The first thing to do is remove the power cable, then hold the power switch and turn the laptop off. Then, using a paper towel, remove excess liquid, using a dabbing action. Don't wipe, as this will spread the liquid.

Swiftly follow by carefully turning it over, keeping the base section horizontal when you've done so, and removing the battery. The focus now should be on drying the laptop. You might do this with a can of compressed air, or a hairdryer on its lowest setting (held around eight inches away).

When you think it's dry, it probably isn't. You'll need the insides to dry out further before the laptop can be connected to the battery or a power supply again. Stand it in an inverted-V shape in a warm room or cupboard, but not on or near a radiator. Do not place the laptop in direct sunlight. You may consider using the rice trick for a smartphone or tablet to absorb the remaining moisture.

Leave the laptop for at least 24 hours, preferably 36 hours, before checking to see if it works. You'll probably find that a new keyboard is required.

4. Regular HDD Failure

Hard disk drives can fail, taking your data with them. Recovery is possible, but it can be a massive obstacle to getting on with the job at hand. It's possible to tell if a HDD is about to fail, just as the imminent death of an SSD can be predicted.

But is it really death?

Corrupted data, bad sectors, a slow PC with regular freezes and the dreaded BSOD can all indicate that your HDD is about to stop for good. But it's always worth checking whether or not the problem lies elsewhere. After all, if there's a chance you can save money on the cost of a new HDD, you might want to take it.

diy computer fixes
Image credit: Simon Yeo via Flickr

While SATA cables are pretty reliable, their predecessor, the IDE cable (also known as PATA), were less so. Similarly, Molex power cables for older HDDs (and optical drives) are also prone to failure. It's not unheard of for an individual wire to come loose from a Molex plug.

In short, before you cast aside your failing HDD, check how it runs with some new cables. You might be pleasantly surprised.

Meanwhile, if your laptop is running out of storage space, consider replacing the CD-ROM/DVD drive with a second HDD.

5. Overheating PC or Laptop

Poor ventilation will increase the heat in the processor, pushing your computer to work harder, and increasing heat. Eventually, the computer will stop. An overheating PC (or laptop) can be avoided by ensuring the vents are kept clear, that the fans are working, and that the inside of the computer isn't clogged with dust.

You can avoid PC overheating issues by increasing the airflow through the case, from the in fan through to the out fan. Reducing obstacles to this flow (e.g. flat IDE cables) is a great fix here. If your motherboard and drives support SATA, that's even better. If you're still relying on IDE/PATA hardware, switch to the type that use a tubular cable rather than the flat "ribbon" variety.

Our guide to installing a new fan in your computer case can help here.

6. Battery Drains Too Quickly

Noticing a quick reduction in battery time on your laptop? Sadly, battery cells don't last forever, and sooner or later you're going to find yourself unable to take your laptop anywhere without a power cable.

But is the battery really dead? Many laptop batteries can be recalibrated, as demonstrated above. If that doesn't help, then it's time to buy a new battery. Replacements can often be bought cheaply, but they're often knock-offs. Wherever possible, stick to a genuine battery from the original manufacturer.

Before you get to the stage of having a "dead" battery, you can monitor its health and hopefully spot issues before they occur.

7. Poor Graphics? Upgrade Your Graphics Card

Poor graphics can be a big problem, especially when gaming or editing video. Frame rates will drop, slowing either experience to a treacle-wading borefest. One way around this is to add a graphics card. They're not cheap (although a decent one can be bought for around $100), but will improve your experience considerably.

What if you already have a good graphics card installed, but the performance has dropped?

This could be related to what is discussed in #5, but if cleaning the dust from inside your computer doesn't help, you have two options. First, upgrade your computer's PSU so that it can cope with the graphics card. You'll need to refer to the documentation of your motherboard and the graphics card (and any other devices with high power requirements) to help you find the right device.

However, it's also worth checking whether the GPU's fan is up to the job. If not, you might consider adding a replacement.

8. Let Your PC Grow

We've already seen how positioning and regular cleaning can keep your desktop computer healthy. But sometimes, it just isn't enough. Could it be that your case is just too small for the hardware inside?

If this is the case, the best option is to migrate the contents to a new case. This is particularly wise if you wish to add storage, expansion cards, or even a new graphics, card. With multiple fans, and increased power requirements, your new case will need to be able to comfortably accommodate the new GPU, along with a larger PSU.

With the right choice of PC case selected, you'll need to set aside at least half a day for this. First timers should view many videos like the one above.

9. It's Just So Noisy!

A noisy computer can be a real problem. It's typically the reaction of the fans to having to expel so much heat. (You can address this by checking the maintenance tips below.) One thing you can check here is the BIOS.

However, that isn't the only reason for a noisy fan. Sometimes, they're just made that way. The hard surface of the computer case might be amplifying the sound of the fan, for instance. It's possible to apply some physical fixes to the fans to keep them quiet.

Such fixes include oiling the fans, or adding foam to cushion the vibration between the fan and the case. You might also opt for a completely fan-less case, perhaps utilizing water cooling, for instance.

10. Can't Get Wireless internet

Getting online still seems to be a problem for a lot of people. One of the biggest issues is wireless internet. If your laptop or PC has built in Wi-Fi connectivity, then this shouldn't be a problem. Often, however, that is not the case.

The first thing you should consider here is the position of the computer in relation to the router. Is there a direct, uninterrupted line of sight? Do you get a better signal when the router or computer is moved? Our tips on wireless feng shui should help here.

However, you should also consider using a powerline adapter if the internet issue is really bad.

All desktop computers (and some laptops) ship with an Ethernet port. Connecting this to a powerline adaptor plugged directly into the wall near your computer, with a similar device at the router end, will overcome any wireless internet problems you're encountering, all without laying cables across the floor.

11. Tower/Case Cleaning

Keeping your desktop computer case (sometimes known as a tower) clean and dust free, inside and out, will improve performance considerably. As noted above, dust and heat combine to reduce airflow, slowing your computer right down. Use a compressed air can and vacuum cleaner to deal with this.

12. Clean Your Mouse and Keyboard

Whether you use an old-fashioned ball mouse, a track ball, or a laser mouse, you'll need to clean it regularly. Sweat and grease from your hand will gather, finding its way into the mouse. Eventually, you'll find buttons aren't working properly. Don't want your congealed skin grease and sweat to make your mouse unresponsive? Keep it clean!

You should also keep your keyboard dirt free. Thanks to the hammering a keyboard gets, this is best done daily or weekly. Tipping upside down and lightly tapping or shaking is one option. You might also try an adhesive removal putty to collect dirt from the keyboard.

13. Smart Positioning

Related to airflow, it is important to keep your computer in a sensible place when switched on. For instance, a carpet in a house with animals is not a sensible place to stand your computer. Similarly, any zone where fresh, cool air cannot reach your PC or laptop should be avoided. There should be space for fresh, cool air to flow into the computer, and space for the warm air to be pushed out. Don't let rubbish accumulate around your computer.

Not only is this a great fix to minimize the dust in your computer, it's a preventative measure that everyone should use.

DIY Fixes Will Save You Money

As useful as these DIY fixes are, they're not always practical. If your computer is leased from work, for example, you might need to rely on your corporate IT department for repairs as part of the arrangement. Similarly, if the computer is bought on lease, you may have to check with the vendor before taking action. Perhaps you're concerned about how much making DIY repairs is going to cost? Well, you'll often need to buy new hardware, but the cost of this can be kept to a minimum.

And then there are laptops. Desktops are far more configurable than laptops, making repairs simpler. In many cases, laptops cannot be repaired, only replaced. Keep this in mind when considering a repair!

Do you rely on DIY repairs? Have you repaired your computer using one of these fixes, or did you try another? Share your fixes, and any other comments, below!