1. Remove spyware and viruses
Spyware collects personal information without asking for permission. Spyware can put your confidential information at risk. Spywares and Viruses can also slow down your computer's performance.
Install an Antivirus to protect your computer from this problems and threats.
ESET NOD32 is my preference antivirus because it is light in memory usage.
2. Free up disk space
You can use the Windows Disk Cleanup tool to free up space on your hard disk to improve the performance of your computer. Other trusted programs are available for free online like CCleaner and Wise Disk Cleaner.
3. Defragment your Hard Disk
When files are fragmented, the computer takes time to search the entire hard disk to access a group of files due to the files are scattered throughout the disk.
Install any free softwares available like Auslogic Disk Defrag.
4. Detect and repair disk errors
Your hard disk may develop bad sectors which slows down data reading and writing or even make it impossible. The Error Checking utility scans the hard drive for bad sectors and marks it to prevent usage of these slots.
Run the Error Checking utility or Windows Scandisk.
5. Detect and repair registry errors
Due to usage and constant Install and Uninstall processes, problems frequently occurs in registry affecting the computer's performance.
CCleaner or Wise Registry Cleaner can be used to check registry errors..
6. Stop unwanted Start-Up programs.
Loading lots of programs at start-up can slow your computer.
CCleaner can be used to view the Start-Up programs and disable those unneeded programs.
7. Set Pagefile size
If your RAM or computer memory is low or less than 1GB, set pagefile to 1GB to 1.5GB.
If your RAM is 1GB or more, set pagefile to 800mb.
Go to Start, (Settings), Control Panel, System. (This is just like the step above this.)
Go to the Advanced tab. Click the Settings button under Performance.
Now switch to this Advanced tab, and click on 'Change' under Virtual Memory.
You will see the 'Initial Size (MB)' and the Maximum Size (MB)'.
Change 'Initial Size' and 'Maximum Size' to sizes discussed above then click set.