Is there a way to register user and password for an account on IIS?
using ( new Impersonator( "myUsername", "myDomainname", "myPassword" ) )
{
   // <code that executes under the new context>
}

//Initialize the metabase path
    string metabasePath = "IIS://localhost/W3SVC/AppPools";
    //Specify the name for your application pool
    string appPoolName = "testAppPool"; //specify the domain account as domainusername
    //Specify the identity that will run the application pool
    string appPoolUser = "User1";
    //Specify the password for the user
    string appPoolPass = "Password1";
    DirectoryEntry pool1;
    DirectoryEntry apppools = new DirectoryEntry(metabasePath);
    pool1 = apppools.Children.Find(appPoolName, "IIsApplicationPool");

    /*Change Application Pool Identity*/
    pool1.InvokeSet("AppPoolIdentityType", new Object[] { 3 });
    pool1.InvokeSet("WAMUserName", new Object[] { Environment.MachineName + @"" + appPoolUser }); //If you are using a local account

    pool1.InvokeSet("WAMUserPass", new Object[] { appPoolPass });
    /*Commit changes*/

    pool1.CommitChanges();