$oldpass = 'XXXXXXX'
$newpass = 'XXXXXXX'
$user = [ADSI]"LDAP://CN=myuser,OU=MyOU,DC=example,DC=com"
$user.ChangePassword($oldpass,$newpass)

$user = ([adsisearcher]"(&(sAMAccountType=805306368)(sAMAccountName=myuser))").FindOne()