1. The disk clean operation must be done regularly. This option is found when you right click on any drives and go to properties option.
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2. Disk Defragmenter is necessary. Go to that option as shown in the picture and right click on drives to defragment them.
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3. Cleaning of Registry. We can't manually clean the Registries so we can use any soft wares as shown in figure.
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4. You improve your start up speed by removing all unwanted soft wares from start up. You go the dialog by typing msconfig run option available in start.
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5. At last keep your system free from all viruses by installing a proper antivirus of original version do remember to update the antivirus for better results.