A computer that runs slowly or takes a long time to start up and shut down can be a massive annoyance and productivity killer. Here are some tips for finding and curing what I know from experience are the most common causes.
Low resources
Every time you add new software, documents or media to a computer, resources that it needs to run smoothly are consumed – disk space, memory space, processor time and network bandwidth as well as less obvious things like registry entries, file “handles”, power consumption and so on. Uninstalling a program or removing a document doesn’t always remove everything. Over time, some of these resources start to run out.
Solution: Use the Resource Monitor in Windows (under Ctrl+Alt+Del > Task Manager > Performance) or Activity Monitor in OSX (under Finder > Go > Utilities) to try to see which resource is causing pain. Often it will be Memory, and adding some extra RAM to most computers and laptops is quite cheap and easy.
Hint: There is a useful system scanner at www.crucial.com for finding the right type of memory for your system. Also, if you need more than 4 GB of RAM you must install the 64-bit version of your operating system, not the 32-bit version.
If there’s a lot of hard disk activity, upgrading to an SSD (solid state drive) can dramatically increase responsiveness and speed, especially at startup and shutdown. SSD drives are now cheap, reliable, silent and use less power.
If 100% CPU activity is the problem, upgrading your processor to one with more “cores” may make a big difference. Check that your power supply can handle it.
Background tasks
It’s common for programs to install background tasks and browser plugins that run constantly and invisibly and do things like informing you when upgrades are available, synchronising your files with “the cloud”, or just allegedly “improving your experience”. Many are useless or positively harmful. In old versions of Windows, the search indexing task and automatic system updater task were common culprits.
Solution: In Windows 10, use the Task Manager > Startup tab or in Mac OSX the System Preferences > Users & Groups > Login Items to disable most items and see if everything still works. Re-enable just the ones you really need.
Virus scanner or infection
Some commercial virus scanners are notorious for slowing down computers, as are the virus infections that they’re designed to prevent.
Solution: Try disconnecting your computer from the network, uninstalling all virus scanners temporarily and restarting the computer. If it’s now running much faster then it’s time to disinfect and look for a better virus scanner (don’t pay money, there are good free ones). Also, don’t forget to scan your computer for “adware”, since advertisements can cause just as much trouble as viruses.
Graphics cards
Graphics cards have their own processor and memory and can slow the whole system down. Also, system drivers for graphics cards are notoriously unreliable.
Solution: Borrow a replacement graphics card and see if that makes a significant difference.
Wake-up events
It’s much faster to start computers from a “sleep” or “standby” state than from a complete power-down, with the added benefit that documents and web pages stay open at the place you were last using them. But many people don’t use this useful feature because laptops take too long to sleep when you “close the lid”, or wake again prematurely.
Solution: On Windows, open a Command Prompt in administrator mode and run the “powercfg” utility to find out what’s waking the machine. Common culprits are mice and network adapters. Then use Device Manager as an administrator to go to the “Power Management” tab for the device and disable the wake function. On Mac OSX, check the Energy tab of Activity Monitor, and try unchecking “Wake for network access” in System Preferences > Energy Saver > Power Adapter.
Other
There are many other possible causes too numerous to list here, including some that are very difficult to diagnose. If your computer ran well in the past but is now slow, there are two solutions that fix nearly all of them:
Solution 1: Restore your system from a backup. On Windows, use the System Restore utility and on Mac OSX use the Time Machine to restore your system from a Recovery Point or backup from a date before the problem started.
If you don’t have such a backup or don’t know when the problem started or it doesn’t make a difference:
Solution 2: Do a “clean” re-installation (or upgrade) of your operating system and programs. This can take a few hours and has to be done with care (make a full backup first!) but is almost certain to succeed. It will clear out any viruses and free up some disk space as well. It’s worth doing every couple of years.