Changing Active Directory user password - language-agnostic

Question

How can I change an Active Directory user password using Directory Services without knowing old password?

Answer 1

You are probably searching the SetPassword method, which you should invoke on a DirectoryEntry object.
Check the "Reset a User's Password" example here: Howto: (Almost) Everything In Active Directory via C#.
EDIT:
If you are having problems with the directory entry being null, you are probably passing a wrong path. The path should be something like this:
DirectoryEntry entry = new DirectoryEntry("LDAP://CN=johndoe,CN=Users,DC=acme,DC=com");

Answer 2

There is a new library introduced in .net 3.5 called System.DirectoryServices.AccountManagement. It simplifies user management stuff.
public void ChangePassword(string dn, string newPassword)
{
using (var context = new PrincipalContext(ContextType.Domain))
{
using (var user = UserPrincipal.FindByIdentity(context, IdentityType.DistinguishedName, dn))
{
user.SetPassword(newPassword);
}
}
}

Answer 3

As an MCSE, I do password resets many times a day so I can tell you something about this.
There are basically two operations you can perform with an Active Directory password - a change, and a reset. Changing a password requires that you know the current password on an account, but resetting a password does not require you to know the current password on an account, so in a way, in order to change a user's password without knowing the password, you really need to perform a password reset operation on the account.
By the way, i believe there are two seperate Active Directory extended rights that control each of these permissions, but I am not intimately familiar with them, as I am a delegated admin who is delegated thos abillity.
So, please keep in mind that any attempts to reset a user's password will fail if you don't have the reset password right granted to you on the target user account.