First of all you need to make sure your computer is free from viruses, Trojans,malware, spyware and other malicious programs since they are mostly the common culprits that make your computer run slow. A spyware , for example, can perform illicit activities without your knowledge by sending hidden data to a specified destination to exploit your system weakness, as a result your personal data such as login details, password, credit card information may be compromised. These malicious activities may render your computer sluggish. So before you proceed , you need to scan your computer with an updated antivirus to make sure your machine is clean. If you have not installed an antivirus on your computer or notebook see the following links to find out more; For Windows/ Windows 7 users : Best Antivirus For Windows 7 , For Mac users : Best Antivirus for Mac. In many instances after you scan and clean your machine for viruses and Trojans your computer is still stubbornly sluggish, and as a result you will still ask yourself “why is my computer still so slow?” follow the bellow instructions to find out the answers.
Delete unnecessary files and programs
The more files and programs you have, the slower your computer will perform, therefore, you need to delete data or programs you do not really need and eat into your disk space. By removing these files you can speed up the computer startup and gives energy to the computer. All computer operating systems come with built-in tools to clean up junk files, such as unneeded Windows files, browser history, temporary internet files, cookies, recent document etc. Many prefer a third party application to clean up those files the simultaneously. One of the most popular applications that can do these tasks is CCleaner, a free yet powerful system performance enhancer that can clean up junk files as well us clean up cluttered computer registry.
Clean up your Desktop
Too many program shortcuts on computer desktop can make your computer sluggish and lose its speed. Try to use the most frequently used program shortcuts only.
Hard drive corrupted or fragmented
Run Scandisk or something equivalent to help ensure that there is nothing physically wrong with the computer hard disk drive. Run disk defragmenter to make sure data is arranged in the best possible order. For Windows 7 See the following link for more details : Windows schedule defrag.
Background programs Slow Down Your Computer
If have an antivirus scanner on the computer, spyware protection program, or other security utility make sure it’s not running in the background as you’re working with your machine . Often when these programs begin to scan the computer it can decrease the computer performance.
Computer or processor is overheating
Make sure that your computer and processor is not overheating, extreme heating can trigger a substantial reduction in computer performance, some processors will even decrease the speed of the processor automatically to help compensate for the heat related issues.
Upgrade your memory
If you have had your computer for more than one year it is likely your computer does not meet the memory requirements any longer. It is , therefore, highly recommended that you should have a computer with at least 1GB of memory to keep up with the latest software updates that require larger memory.
Not enough hard disk drive space
Make sure that you have at least 200-500MB of free hard disk space. This available space allows the computer to have room for the swap file to increase in size as well as room for temporary files. Delete unnecessary large files such as videos and other multimedia files.
Hardware conflicts
Verify that the Device Manager has no conflicts and make sure you have installed the most up-to-date drivers for your computer hardware, specifically the latest video drivers. Having out-of-date drivers may lead to various computer issues.
Hardware issues can also make your PC slow
If your computer continues to be sluggish after implementing each of the above suggestions it is likely that the computer is having a severe hardware-related problem like a failed component in the computer. This could be a flaw or faulty or other component that stops to work.
Last Resort : Reinstall computer
Lastly, if not any of the above-mentioned solutions solve your problems, it is suggested that you reinstall your computer and start over.
I hope that after going over the above step-by-step instructions you will be able to get your computer back to its peak performance, run faster and not ask again the question why is my computer so slow 