There are tons of reason that would make your computer to respond slower than expected, such as system capacity, hardware problems, operating system files corruption, network problems, driver problems, applications problems, viruses, etc. In this article, we will point out some of the things that you could check and maybe fix your computer from been slow.
1)
System Capacity: this simply refers to if your system is lacking resource such as memory, CPU or hard drive space to efficiently run all your application needs.
a) To find out the computer memory and CPU power, click
Start, right click
Computer, and click on
Properties

b) View your memory size, CPU type & speed. Upgrade your memory if there is need.

c) Ensure that there is enough Hard Drive space available for the swap file to increase in size as well as room for temporary files. To check your hard drive space, click
Start, click on
Computer, right click
drive (c:), and click on
Properties. Do a Hard Disk cleanup to free up space on your computer, see
Disk Clean article to see how to perform this.

2)
Hardware Problem: ensure that your computer does not have bad hard drive sectors or other hardware failure. Run system diagnostic tools to check for any hardware issues. Depend on your computer model; there are factory specific diagnostic tools and generic system diagnostic tools that you can use to ensure that your system is not failing for hardware. You can also run windows ScanDisk and chkdsk command to diagnose your hard drive.
3)
Operating system files corruption: a corrupted operating system will cause your computer to a halt. If you suspect your operating is unstable, run a windows repair. To run windows repair, boot the computer with your original Windows CD and choose the repair option or press R to repair.

4)
Network problems; slow internet or network connectivity while the other applications are responding fast is indication of bandwidth or network card problem. Check to see if you have enough bandwidth for your upload, download and browsing needs. Also, verify that your network card has correct driver installed and free of errors.
5)
Driver problems: drivers are software that operates between your hardware and operating system. It's important to have correct drivers for all your hardware components especially the Graphic Card and Network Card. To check computer drivers; click
Start, right click
Computer, click
Properties and in the System Properties window, click on
Device Manager. Ensure that there are no missing drivers or wrong drivers installed.

6)
Application Problems; if you notice slowness when you run an specific application, it's possible that this application requires greater resource than the computer can handle, not compatible with the operating system, not compatible with the operating system version, or another application, or there is some type of application development problem. Check the application developer for updates or fixes. Remove start up programs that would run in the background.
7)
Viruses & Malware: virus, spyware and other malware is another cause of computer problems. Update your Anti-virus program and perform boot scan, deep scan or full scan of your system. If you don't have commercial anti-virus installed, you can use free anti-virus programs such as
Avast Free Anti-Virus. Also, install and run malware removal program.
Walwarebytes is good free program that you can run on your system for spyware and malware.
Few other things that you can do to optimize your computer
1)
Run a Disk clean
2)
Run Disk Defragmentation
3)
Remove programs from the system start-up
4) Reboot your system regularly
5)
Remove browser add-ons from your browsers
6)
Perform operating system updates regularly
7)
See what programs or applications are using most of available memory & CPU
8)
Choose good optimum anti-virus program - Some anti-virus program consume more resources that could slow down your computer
9)
Check your hard drive for errors