Bonjour (Hello in french) I follow the advices that Tesla1856 and Da_Vinman gave me some weeks ago ! Merci beaucoup à tous les deux ! (I thank you very much you both) Sorry for my very bad english I changed the 500GB HDD for a 1TB SSD I put an additional 4GB RAM memory on the free port (total 8GB instead of only 4GB) A cleaned all the sand (it was totally jamed) that was in the fan and heatsink I bought the licence and installed a Windows10 Pro 64bits (licence very cheap on amazon germany) Now, I have got a very quiet PC, and I am impressed by the result ! Everything is going much more faster than before ! I am not affraid to write that I am the owner of a brand new PC !!! Once again, thanks for your help !