Dell vostro 3500 overheating

Hi, I have a dell vostro 3500 and it overheats very bad, even after applying new thermal paste and cleaning the fan and vents it still overheats even if i am not doing anything at all.

I tried to disable turbo boost but power settings in bios is locked in this model so i used an external software called throttlestop which allowed me to disable turbo and the temperature decreased after that but now how can I fix this issue without using an external software ?