Operating systems come with their own set of small application tools that help users figure out any computer problems. These tools can scan local hard disks, manage devices and their properties, reset system configurations, check the network connections and basically tweak various aspects that affect operation. Of course, it can happen that these built-in tools may not be enough to troubleshoot a particular problem. In such instances users may resort to using third-party troubleshooting software. The internet is the most easily accessible and richest source of such third-party tools.
Most users know enough not to download the first troubleshooting software they find on the web, but this is such an important point that it bears reiteration. There are no rock-solid guarantees with third-party software (for that matter you can never be completely sure with built-in tools either). Such tools are designed and developed by individuals or groups. Some of them do it for a living; others do it as a hobby. As with anything software related, compatibility is almost always the main issue. Much of the potential hassle can be avoided with a little prudent research. There are a lot of sites such as forums that focus discussion on computer problems and repair. Most of them group around particular operating systems - Windows, Linux, Mac OS, etc. Reading through them or even actively participating can be very informative. You can easily get reviews and recommendations on which troubleshooting software is best for what problem on what system. Afterwards you can further educate yourself by actually reading any available documentation on the software. You can usually find such manuals on the homepages, but remember that not all developers are fastidious enough to actually provide user-helpful documentation about their creations.
When attempting to fix computer problems on your own, you're going to necessarily make a few initial guesses. Depending on how proficient or familiar you are with your system, these assumptions could lead you closer to a solution or do just the opposite. That's why the first step in troubleshooting is always diagnosis. Most built-in and third party tools are diagnostic in nature. They evaluate a certain property and report information. It is obviously necessary to first figure out what the problem is before you can decide which tool to use, and diagnostic software is key to helping you isolate the problem. You don't need a system registry editor if the problem lies with some bad sectors on your hard disk. But to have known this you would need to first apply a disk scanning tool.
A significant amount of computer problems actually stem from viruses and malware. Antivirus and anti-malware programs can thus be also considered troubleshooting software. These applications are easier to use, as once installed they are by default on standby mode, regularly checking your system for any irregularities. They provide both diagnostic and repair functions, but to be effective their database needs to be consistently updated.