Given the wide range of computers and their devices in use today, no single article can describe how to fix all of the potential hardware issues one might face. But I can discuss numerous guidelines and tips, in order to avoid — or at least minimize — the time, expense, and frustration involved in tackling hardware problems.
In the Beginning
If possible, first make multiple backups of all your data. That way, if you accidentally damage your hard drive, or if you must get a replacement machine, at least you'll have a full backup of everything. Otherwise, Plan B won't be an option. If it's a PC you're fixing, record your system's BIOS settings, especially if you tweaked them at some point.
Before disassembling your machine, give yourself plenty of dust- and static-free space in which to work. A cleaned-off table is much safer than the Dust Bunny Zone on the shag carpet where the poor computer usually resides. In the heat of the moment, it's easy to get too creative with places to temporarily place items. Do not rest cards or chips on or near CRT monitors, phones, or speakers — all of which are sources of magnetic fields.
When your machine is disconnected from its cables, and opened up, it's the ideal time to remove the dust that has accumulated inside the box and on the fans. That dust reduces the dissipation of heat from the components, increasing their odds of failure. Use a soft brush attachment on a vacuum, or a can of compressed air (with the straw). You will probably want to do this outdoors, especially if the inside of your machine looks like an archeological dig. But before powering down the computer, close all disk trays and remove any diskettes that are partially ejected, to avoid getting any dust inside the CD, DVD, or diskette drives.
Most techs will insist that, during open-machine surgery, it is safer to have the power cord disconnected from the power supply unit (PSU); others will argue that the power cord provides grounding. Many experts recommend disconnecting first, and then waiting a minute for any charge to cycle out. Has your PSU stopped working? Or, more dramatically, did it seemingly explode — blasting a cloud of dust several feet? (Some components refuse to go out with a whimper.) Don't even think about repairing it or opening it out of curiosity (remember what happened to the cat…). The voltage inside is too dangerous, and not worth the risk.
Not only do you want to avoid electrocuting yourself, but beware of accidentally zapping a component with static electricity from your hands. Either wear an anti-static wrist strap, or touch a grounded metal object every time before touching any component, to discharge all errant electrons.
Obviously, don't open your computer or swap parts or peripherals, while the unit is running. That includes (dis)connecting keyboards and mice. If you have a programmable keyboard, that's the surest way to lose the settings in its memory. Even a traditional keyboard will likely misbehave if reconnected to a running PC. Only video cables and audio speakers seem immune from that rule.
The insides of most PCs are already cramped with cards, cables, fans, and power lines that appear to increase as systems get more sophisticated. Do not hesitate to give yourself more working room by temporarily removing cables or gently tying them out of the way.
Before disconnecting any ribbon cable, record at which end the number 1 wire connects, unless it's clearly marked on the board or device, or unless that end of the cable can only connect in one way. Also, if you do not feel completely confident that you will remember exactly where every tab A fits into slot B when reassembling, then record where each cable belongs in a simple diagram, or label the end of each cable and its proper corresponding slot.
Don't force anything. If it doesn't fit, then there probably is a good reason why. That's not to say that you won't have to make some slight "enhancements" to the components or, even more commonly, the case itself. But applying force is the exception. It is the most common way of breaking or bending a connector, pin, diode, etc. For some sensitive parts, bending them is just as bad as breaking them. (I am talking about computer hardware…) In addition, do not use excessive force downwards into the motherboard when installing memory and peripheral cards. Over-flexing a board can cause hidden and lethal cracks.
If your computer makes a beeping sound when you boot up, and you don't get a video signal, then there is something wrong with your motherboard. First check the clock battery, since those usually last only a few years. Then check the on-board memory cache, which can get fried from electrical static shock. Then check the RAM (system memory), one module at a time. The sequence of beeps should be explained in the motherboard manual or on the manufacturer's website. If your computer does boot fine, but its clock does not keep time after a reboot, then the motherboard battery is dead.
Part swapping is an effective way of isolating the source of a hardware problem. For instance, if you suspect a particular memory module to be the culprit, try each module in a second, working system, to find out exactly which one needs to be replaced. This is one of many good reasons for having a second computer. At least, that's what you can tell your spouse…
Now some brief component-specific suggestions: When removing or adding a hard drive, loosen the screws of all the other drives in that same 3.5" bracket, to make room. Before replacing a new video card, uninstall your existing video card drivers before pulling out the old card and installing the new one. Otherwise you can have endless problems in Windows.
Without a doubt, the best way to "solve" a computer problem is to avoid it in the first place. When it comes to hardware, this can take the form of research into which manufacturers have the best reliability records and longest meantime between failure (MTBF) ratings. Prevention is definitely the best cure.
Along the same lines, to minimize time spent fixing hardware difficulties, choose a computer that makes it as easy as possible to modify its innards. Look for such features as thumb screws (not the medieval kind), side panels that pop off easily, motherboard trays that slide out, drive racks that swing out, and clamshell cases that open up like, well, a clamshell.
Last but not least, to minimize scratches, ripped fingernails, and bloodshed, pay extra for quality cases, without sharp metal edges and burrs. If you are building your own system, it is worthwhile to inspect the case interior for such dangers, and simply file or sandpaper them down. Months later, when you are jamming a finger between two metal brackets to push in an errant connector, you'll be thankful you spent the time removing the dermal dangers. Minimizing blood loss is as important as avoiding data loss.
Here's hoping all your cyber surgeries prove successful!