check for duplicate rows

[lJesterl]

I'm working on a page that selects id, alias, and ipaddress from table users and it then lists it to a webpage. I worked everything out and it post my table to the website and sorts by IP. Exactly how I want it to. The only problem is that im trying to get it to list DUPLICATE in the <td> beside the ip address so that I can see when viewing my user database wich accounts are duplicate ip's. I am farely new to php and I'm not sure what the value to X in my code should be or if i should use a different method. Any help would be great. Here is a snip from some of my code.

$getipinfo = mysql_query("SELECT * FROM users ORDER BY ipaddress ASC");
while(list($id,$alias,$pass,$email,$icq,$aim,$yahoo,$website,$logo,$newsletter,$joindate,$ipaddress)=mysql_fetch_row($getipinfo)){
$ip=mysql_query("SELECT ipaddress from users");

$iconlist="";

if($ipaddress =="[color=red]x[/color]")){
$iconlist=$iconlist."<font color=#FF0000><b>DUPLICATE</b></font> ";
}

$userlist = $userlist."
<tr>
<td bgcolor=202020>$id</td>
<td bgcolor=202020>$alias</td>
<td bgcolor=202020>$ipaddress</td>
<td bgcolor=202020>$iconlist</td>";
$userlist = $userlist

[lJesterl]

=[

[samshel]

What output do you get ? Can you paste the HTML you get in the View Source of the page ?