Dealing with a slow computer

Someone on our private Word of Mouth site asked about dealing with an old slow Mac computer, that used to be much faster. I hate it when it does that! Honestly, I always get awesome results with a brand new computer, but it sounds like that’s not an option, so here goes:

In some cases, slowness comes from a bloated system, which can have different causes. Here are some of the things that slow a system down:

• Recent system changes can be the cause of a misbehaving system. The first thing to think about, is whether or not any changes have been made recently. If so, start by double-checking those changes, to see if they caused the problem. This can be the introduction of a new operating system, application software, or even just a system setting change that has a significant and unexpected effect.
• A hardware problem can cause a system to run slow. Sometimes an incompatible memory card, or other circuit card has been added to a system, which causes the system to work very hard to deal with a high level of bus or other errors. If a hardware change has been made recently, one thing to try, is to remove that new hardware, to see if it resolves the problem. It's also possible that an existing piece of hardware has partially failed, and is causing problems. That's harder to diagnose, but often there are clues that can lead you to the problematic hardware, if you're paying attention.
• An overfull system drive. This is easily diagnosed, with a high level disk status, that shows disk size and available space. An overfull drive is often caused by one or many large files on the system that don't need to be there. The best way to find these files, is to use third party utility software such as TreeSize Free, that can list all the files on the computer, sorted by size. An overfull disk can be also caused by a large amount of legitimate user data (pictures, music, videos) that has accumulated over time, in which case managing that data becomes the issue. You can identify your older unused data, and move it to external storage, to free up space. The simplest solution is to add a new larger hard drive to the system, or add additional storage some other way, such as by subscribing to Cloud storage, and move some or all of your user data to the new storage location.
• Overly full memory (RAM). This could simply be a case of not enough memory for the job the computer is now being asked to do. Operating System and application software updates often bring with them the need for more memory, just because the programmers have added new features. The simple solution is to add more RAM to the system, by carefully researching compatible memory. It can also be caused by unnecessary software running in the background.
• Corrupted system settings. Most older systems have suffered through myriads of system setting changes over the years, some of which cause the system to be looking for items that no longer exist. There are lots of third party software tools out there, that have the ability to scan your system for this type of problem, and help to clean out old obsolete system settings. I highly recommend a complete system backup, before giving this software the permission to change your settings, because they sometimes make changes that make it difficult for the system to work well, or sometimes, it can't work at all after the "repairs."
• CPU busy all the time. This is usually caused by unexpected software running in the background, but is also the symptom of a system that is running low on memory, and working very hard to use the available memory as efficiently as possible. Unexpected software can include benign software that came with other software, such as daemons whose job is to watch for available updates to installed software. There is also the danger that unexpected software is malicious software (malware) that is taking advantage of your system resources, to perform tasks that are entirely undesired. It is the job of good antivirus and anti-malware software, to find and eradicate malware, so make sure your system is running it.

You can spend a lot of time chasing down each of those individual issues, but my best results over many years of owning computers (Macs and PCs) at home, and developing software & doubling as a system administrator at work, have been with a complete system reload from scratch, starting with formatting the hard drive, installing the operating system from the original disks (or the network, if your computer can do that), then adding applications back (only the ones you need), and finally, restoring your personal data from backups.

This can be a daunting task, if you use many applications, and have a tendency to modify many system and application settings from their defaults, to make the system work better for you. However, every time I‘ve done this, my system has come up running way faster, for years afterwards.

Most importantly, keep a written system log, and from the moment the disk is formatted, make note of every significant change to the system, whether it is addition or deletion of hardware or software, or a system or application setting change. The system log is your most valuable tool, in identifying what changed, just prior to the system misbehaving.

Here's something that I found on the Web (of course there is much more like this out there), that sounds like some legitimate things to try.