Pretty much the best way to speed up a pc apart from installing an SSD is to perform a clean install of the operating system. Cooling also effects speed. The thermal paste on the back of the CPU normally wears off in time and needs replaced. This is only possible if your CPU is not soldered onto the motherboard. Adding RAM could help depending on what tasks the laptop is used for and whether or not the ram is soldered onto the motherboard. But you need to decide if upgrading is both worthwhile and cost effective versus buying a new laptop.
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