Firstly set Control Panel to "View By Small Icons" as more options will show up.
1) Set System Restore Space
Location:
Control Panel >> Advance System Settings >> System Protection >>Configure
Set the System Restore to use less Disk Space so it will not "eat up" additional Harddisk Space as time passes.
You can also use this to set/delete restore points.
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2) Set Performance Visual Options
Location:
Control Panel >> Advance System Settings >> Advance >> Performance Options
Uncheck the Options as shown below while leaving the rest untouched:
3)Uninstall Unused Features
Location:
Control Panel >> Program & Features >> Turn Windows Features On or Off
Uncheck unused Programs like "Tablet PC Components" and "Windows Media Centre"
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4)Disable Unused Devices
Location:
Device Manager
Right Click and Disable rarely used Devices to reduce System Device Polling and conserve power.
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5)Set Advance Power Options
Location:
Control Panel >> Power Options >> Edit Plan Settings
Customise Power Plan settings according to your preference
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6)Defragment and Disk Clean Up