end user registration problem?

Hii friends ..
I am doing front end user registration and login..
in that i have to allow only one registration for one email id ..
for that i am checking database by using the following query..

$count=0;
$count=$wpdb->query(“select count(*) from $usertable where email_id=’$email'”);

but the count variable is automatically setting to 1 with out form submition..
please help me regarding this

thanks in advance..

http://wordpress.org/extend/plugins/dashboard/