Okay, but we need little bit more information:
Here is the screen:
As you can see each filed of the form has unique ID, so you need to send us, something like
user_id = Form field ID 6
user_name = Form field ID 3
user_passwd = Form field ID 1
user_group = Form field ID 2
user_email = Form field ID 78
I hope it's can help
Regards,