>Thank you Al
>
>1-I already googled for some utilities and found TrueCript.But i am stopped in this page
>http://truecrypt.sourceforge.net/
>by a warning message:
>WARNING: Using TrueCrypt is not secure as it may contain unfixed security issues
>This page exists only to help migrate existing data encrypted by TrueCrypt.
>
>2-Panneau de configuration\Système et sécurité\Chiffrement de lecteur BitLocker
> (control panel\security system\...Bitlocker)
>yes it exists on my windows10 but its appliable to whole disc (as c:\,g:\ ,f:\..)
>its also appliable to amovible disc (insert USB to apply Bitlocker To Go).
>it locks or unlock the whole drive by password.
>
>i want just lock/unlock a special personal folder.

You could put your "special personal folder" on a USB stick used only for that purpose, and use BitLocker for that.

Re TrueCrypt: You might want to read the Wikipedia article. It explains the current status of TrueCrypt and lists a couple of alternatives, which are forks of TrueCrypt. It also explains some limitations of any software-based encryption; in that regard you can never get 100% guaranteed security. But maybe one of those products will be "good enough" for your purposes.