Why is my computer slow? (3/18/09)

If you were having car trouble, would you open the hood, change something (perhaps on the advice of a well-meaning friend), and hope that it would fix the problem? Would you try a fuel additive because the ads made it sound good? Or would you work with your mechanic to collect the symptoms, identify the most likely problem, and find an appropriate solution?

In my previous career as a software engineer I learned from some very smart and experienced people that in order to figure out why a computer is running slowly, it's important to be observant and methodical, to measure whenever possible, and not to assume you know where the problem is. That was good advice for PDP-11 minicomputers built in the 1970s, and it still applies today.

What do you mean by "slow"?
There is no single universal solution to speeding up a computer. Carefully observing when it runs slowly will help focus the diagnostic effort and get you to a solution sooner. For example:

Is it slower than before to start up? In my experience, powering on the average computer that's fully turned off (not waking from sleep, standby, or hibernation) takes about 3 minutes to start up and be ready for use. A significantly longer startup time (more than 5 or 6 minutes) might mean the computer has excess startup software or not enough memory, but it also might be an issue with the keyboard or mouse, or something external, such as a problem with the internet connection.
Is it slow to respond to clicks? Is the time between clicking on an icon and that icon becoming selected more than a fraction of a second?
Is the slowness predictable or intermittent?
Does it occur right after the computer starts up, or at a later time?
Is it slow to open a particular program or document?
Once open, does the program operate slowly? Does this occur in some programs and not others? Is there a pattern, e.g., only with programs that access the internet, or only when you print?
Can you hear the hard disk churning or clinking away when it's slow?
Is it slow to shut down? Windows Vista can appear to be "stuck" during shutdown while it's installing important updates, but since it doesn't tell you what it's doing, you might think it's a problem when it's not.

Speed or slowness can be very subjective, so being methodical and specific, and measuring the time with a clock is a useful place to start.

I've got good news and I've got bad news
The good news: While many things are possible causes of a slow computer, only a small number of things are the most frequent, often occurring in combination:

Too much running software (often launched at startup)
Too little RAM
Issues with your internet connection

The bad news: These can be difficult for the average person to correctly identify and solve on their own.

Why do computers become slower? More likely reasons
Like a car, a computer has many important resources, so when one or more of them runs low, it can slow the entire computer down. For example:

Slow to start up: On Windows, many software packages (including Microsoft Office, Adobe Reader, and Quicken) install startup programs to "pre-load" a portion of their package to save time later, but if you don't use the software, their pre-loaders waste some of your startup time and your RAM. Many packages on Windows and Macintosh also install startup programs (updaters, alerts, reminders, etc.), many of which also waste your startup time and RAM.
Too much running software: Whether they launch at startup or later, when unnecessary programs are running, your computer is busier and has less available RAM. Many little programs run "behind the scenes" all the time, some are necessary (services for your clock, printer, hard disk, mouse, keyboard, antivirus, etc.), some are unnecessary but benign, and others may be viruses or spyware. Also, you may open programs, finish with them, but leave them running. For many computers this is no problem, but for some this can cause a slowdown. However, programs that are installed but not running don't contribute to this problem at all.
Not enough RAM: The Random Access Memory used to "run" software is a fixed size. If there isn't enough to hold all the running software, the computer turns part of your hard disk into "overflow RAM," enabling the software to run but at a much slower speed, since it has to "swap" programs between regular RAM and your hard disk.
Slow internet: If your internet connection seems to be the source of the slowness, don't upgrade to a faster level of service just yet. There are a number of potential causes which this won't fix, including poorly adjusted internet software, wiring problems, wireless signal interference, and using wireless when a "wired" connection would be more appropriate. Asking Comcast or Verizon to solve your internet speed problem is like asking your gas station what type of fuel you should buy--both will likely sell you their premium product without looking at your actual needs.
Combination of problems: Sometimes there are multiple reasons a computer is slow. Solving the most significant problem enables you to uncover the next-most-significant one.

I had a client whose older Windows XP computer took 30 minutes to start up, measured from pressing the power button until the hourglass cursor stopped. This didn't occur overnight, it took years to get this bad. I found that it had an unfortunate combination of problems: It had too little RAM (128 megabytes) and far too many startup programs, accumulated over many years, not to mention the growth in the size of Windows XP itself. After I increased the computer's RAM to its maximum (512mb) and trimmed the startup list appropriately, the startup time dropped to about 3 minutes.

Why do computers become slower? Less likely reasons

Hard disk too full: Many users incorrectly assume this must be the problem and think they have to clean out their computers, but it's really rare. If you're concerned about this, learn how to measure the space (in megabytes or gigabytes) your data takes up vs. how much space your hard disk can hold, and you'll probably find that it's not a problem. And while deleting temporary files and emptying caches is good maintenance, it probably won't make your computer faster. Don't assume you've got a trunk full of cinder blocks, find out for sure!
Hard disk too fragmented: Imagine a shelf of books whose bindings have been removed and all the loose pages are scattered about. In order to read the pages of a given book in order, you must "jump around" the shelf, reading page 1 here, page 2 there, etc. This is why a severely fragmented hard disk might be slow. Defragmenting gathers together the "pages" of each "book," in order, making those "books" more efficient to read. However, fragmentation that actually causes computer slowness is also rare, except when frequently-accessed hard disk items become fragmented, such as that hard disk "swap" area mentioned above.
Hard disk wearing out: Hard disks use magnets to read and write a large number of tiny spots to store their data. When some of those spots start to fade, the first attempt to read them may yield gibberish, but second or third tries work. Over time those spots require more and more retries, taking more time, until they finally exceed the hard disk's retry limit and become unreadable.
Inadequate processor (CPU) speed, older computer, etc.: Sometimes a computer is simply underpowered for the software you're trying to use. Trying to tow that yacht with a Geo Metro just won't work.

What usually doesn't help
There are many things you might be tempted to try, including:

Defragmenting the hard disk frequently.
Removing software you might think is unnecessary or taking up too much space.
Removing data you might think is "clogging up" the computer, especially if you think you have "too many" documents, photos, web favorites, etc.
Buying or downloading "fix-it" software that promises to "clean out" or "tune up" or "supercharge" your computer.
Paying your internet service provider more per month to upgrade you to a faster connection.
Trying the solution that worked on someone else's computer.

At best, such attempts do no particular harm and may address one or two specific issues, but they're more likely to waste your time and money and add more unnecessary software to your computer. They may also increase the "wear and tear" on your computer and, at worst, render your computer unusable. My advice is to avoid leaping to a solution without first identifying the problem and then working to isolate its cause.

Years ago I had a client who was besieged by a constant barrage of pop-up ads, so he installed a pop-up blocking program to suppress them. This hidden battle took up most of the computer's attention, slowing it to a crawl, and was only resolved after the many advertising programs were removed.

Where to go from here

Try shutting your computer down (not sleep, standby, or hibernation), then turning it back on again. Computers can get a little stuck in the mud, especially if they've been running for a long time, and this can help get them back on the road, at least temporarily.
If you use Windows, your antivirus software should be working and up-to-date, and you should also do full antispyware scans regularly; two good sources of antispyware programs are http://www.SuperAntiSpyware.com and http://www.WindowsDefender.com, both free. On Macintosh, it may be time to get an antivirus program; one I like is the commercial product VirusBarrier from Intego (http://www.intego.com/virusbarrier).
Try to gather specific (ideally, measurable) observations about when it's slow.
Talk to a computer professional about the problem. If it may take a lot of work to fix, also discuss the cost of fixing the problem vs. replacing the computer.

Approach this like you might approach a problem with your car--learn more about how to identify and describe the problem, try not to assume too much, and work with your mechanic to find a reasonable solution.

If you know someone who might find this helpful, please feel free to forward it.
If you have any comments about this article, send me a reply!
If you have a topic that you'd like me to write about, I'd love to hear about it!

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