Answered Login Registration - check that username is not already in use

<h2>Register</h2> 

[[!Register? 
    &submitVar=`loginRegisterBtn` 
    &activationResourceId=`34` 
    &activationEmailTpl=`lgnActivateEmailTpl` 
    &activationEmailSubject=`Thanks for Registering!` 
    &submittedResourceId=`33` 
    &usergroups=`registrants` 
    &validate=`no spam:blank,
    username:required:minLength=^6^,
    password:required:minLength=^8^,
    password_confirm:password_confirm=^password^`
    &useExtended=`0` 
    &postHooks=`ExtUserRegisterPosthook` 
    &placeholderPrefix=`reg.`]] 
   
<div class="register"> 
    <div class="registerMessage">[[+error.message]]</div> 
       
    <form class="form" action="[[~[[*id]]]]" method="post"> 
        <input type="hidden" name="nospam:blank" value="" /> 
           
         <label for="username">[[%register.username? &namespace=`login` &topic=`register`]] 
            <span class="error">[[!+reg.error.username]]</span> 
        </label> 
        <input type="text" name="username" id="username" value="[[+username]]" /> 
          
        <label for="password">[[%register.password]] 
            <span class="error">[[!+reg.error.password]]</span> 
        </label> 
        <input type="password" name="password" id="password" value="[[+password]]" /> 
           
        <label for="password_confirm">[[%register.password_confirm]] 
            <span class="error">[[!+reg.error.password_confirm]]</span> 
        </label> 
        <input type="password" name="password_confirm" id="password_confirm" value="[[+password_confirm]]" /> 
           
        <label for="email">[[%register.email]] 
            <span class="error">[[!+reg.error.email]]</span> 
        </label> 
        <input type="text" name="email:email" id="email" value="[[+email]]" /> 

        <label for="firstName">First Name</label> 
            <input type="text" name="firstName" value="[[!+reg.firstName]]" /> 
        <span class="validateError">[[!+reg.error.firstName]]</span> 
  
        <label for="lastName">Last Name</label> 
            <input type="text" name="lastName" value="[[!+reg.lastName]]" /> 
        <span class="validateError">[[!+reg.error.lastName]]</span> 

        <label for="primaryPhoneNumber">Primary Phone Number</label> 
            <input type="text" name="primaryPhoneNumber" value="[[!+reg.primaryPhoneNumber]]" /> 
        <span class="validateError">[[!+reg.error.primaryPhoneNumber]]</span> 



        <br class="clear" /> 
           
        <div class="form-buttons"> 
            <input type="submit" name="loginRegisterBtn" value="Register" /> 
        </div> 
    </form> 
</div>

<span class="error">[[!+error.reg.username]]</span>