Before all "merci beaucoup" (thank you very much in French) !!!!!
So, I understand that the best to do (to avoid a waste of time), is to put a SSD instead the HDD, and probably 4GB RAM more (total of 8GB of RAM : I have actually "only" 4GB).
My aim is to format and install a clean Windows 10 instead of Windows 7 64bits.
Even for this (Windows 10), the 4 cores CPU (instead the twin cores CPU) is not so efficient ????
Once again, thanks in advance.