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.