WordPress MU

Is there any way out that all new registrations must create a blog and they donot get an option just to register a username on the home blog?

Try editing wp-signup and removing

<input id="signupuser" type="radio" name="signup_for" value="user" <?php echo $signup['user'] ?> />
<label class="checkbox" for="signupuser"><?php _e('Just a username, please.') ?></label>

Thanks for your reply but i want to remove the complete option. Can there be any trouble if i remove the html code for both the options?

You'll still need the the input, just change it to hidden.

http://htmlhelp.com/reference/html40/forms/input.html

although i knew this can be done but wasnt sure if it may cause any troubles on the signup page while validation but worked fine

thanks