is possible to set a password to a registry key?or block acces?

is possible to set a password to a registry key?or block acces only for that key?do not let that no one can edit or delete

Registry is treated exactly the same as the file system, each key and value has its own permissions so that each user can only view or modify only a subset of it. Normally every user has read-only access on HKEY_LOCAL_MACHINE and HKEY_CLASSES_ROOT but full read-write permissions on HKEY_CURRENT_USER. Administrator have of course unrestricted access to everything.
Like any other file, you should user normal permissions and different accounts to protect sensitive parts of both registry and filesystem.

Layback Bear said:

If the users does not have admin privileges they will not have access to the registry to the best of my memory.

Only to part of it, according to the permissions given to each one.
The built-in registry editor (regedit.exe) always request admin access when using the default setup, but it's not strictly needed. Admins have access to everything, but plain users still have control over their own settings.