Pc slowed down, how to fix it?

try to reset your bios by selecting ( load optimal setting ) then restart ... dont change anything in your bios that y dont know couse it might make unrecoverable error or it might damage your bios ....... try to use some registry cleaners like : cccleaner ..... and clean yr fans inside from dust .... try keeping yr case cool by add some thermal past to yr processor .... the more cooler the more stable yr system will get .....