Pay close attention to this Trade Secret if you plan to change hardware inside the computer case. No, we're not going to tell you how to make internal hardware changes - there are far too many computer and component designs, and the information you need is already available.
Before you begin, learn everything related to your planned change that you can from your computer and hardware component manuals, help files, and the manufacturers' websites.
Check for compatibility issues between components, physical and space measurements, power requirements, special procedures, settings, and software, and the required sequence of steps for installation or removal.
If you're reading this page, you may already know this much. The only thing we want spell out for you here are the important rules of safety for you and your computer.
This page mainly refers to desktop computers. The safety information is also useful for notebook ("laptop") computers, but you should not open the case of a notebook computer without explicit instructions and a specific reason for doing so.
———•———
Before you open the computer case
Backup your System and personal data. (You only have to backup the stuff you don't want to permanently lose!)
Shut down the computer. Never open the case while the computer is running. If you do, you risk harmful or fatal electrical shock, eye damage from laser radiation, and serious damage to the computer. In addition, some computers have internal safety switches which cut power if the case is opened, resulting in a hard system crash.
Next you're going to unplug some things. If you're concerned about forgetting which plug goes where, write the location on a mailing label and stick it on the cable. Remember to give external hard drives at least 10 seconds to completely stop spinning before you unplug them.
Shut down all external hardware that is connected to the computer. Locate all external hardware which has its own power supply, including the monitor, and physically unplug its power source, then unplug the hardware from the computer. This equipment may contain components which store a charge, even with the power shut off. Now physically unplug the computer from its power source.
You may not appreciate all this extra work. Maybe you put a lot of effort into arranging your setup, all the cables are neatly tucked away, and everything is plugged into a power strip; so you can just turn off the power strip and be safe, right? True - and the chance that the power strip will look like it's off, when it isn't, is one in a million. If you like these odds, go buy a lottery ticket. Then come back and unplug the stuff.
Use a grounded wrist strap to ensure you aren't carrying a static charge which can damage delicate components. You can get by with touching grounded metal periodically while working, but certain clothing can quickly build up another charge.
Make sure that none of the tools you will be using on the computer are magnetized.
After you open the computer case
Use a small, properly grounded or battery operated, low power vacuum cleaner to remove dust inside the computer. Don't let the cleaning tool tap on the components.
You can also use "canned air" to blow out the dust, however: make sure the work area is well ventilated because this air isn't for breathing. If you have an internal optical drive, canned air may blow dust or hair onto the laser lens, causing errors when reading optical disks.
You should regularly clean inside to prevent heat build up, electrical arcing between components, and obstruction of cooling fans. While you're at it, clean the keyboard and mouse (canned air is fine for these), and other external devices.
Don't use excessive force when changing hardware. It's better to temporarily remove an extra part to provide clearance than to break a connector on your hard drive. Cards, chips, and plugs need to be seated accurately and firmly, using available latches, screws and clips; but if something doesn't assemble easily, recheck that you have the right parts, and that they are properly aligned.
After the surgery
Generally speaking, reconnect everything in the reverse order in which it was disconnected; power sources should be connected last. Make sure that exposed metal on the plugs of unused internal cables cannot inadvertently touch other components. When replacing the cover on the computer chassis, ensure that no internal cables become trapped in the casing.
Follow the manufacturer's instructions for installing new hardware and accompanying software. Then fire everything up, test the new components, and watch for impact on other components and overall system performance.