find machines with duplicate serial numbers

I have this SQL code to try and find machines that share the same serial number.   when I run this it only retruns 1 record and we know for a fact we have many dups.  We're doing a rollout from XP to Windows 7 so we end up with serial numbers attached to 2 or 3 NetBIOS names.
 
SELECT 
cs.Name0 AS [Computer Name],
rs.User_Name0 AS [User Name],
rs.User_Domain0 AS [Domain],
gs.SerialNumber0 AS [Serial Number]

FROM v_GS_COMPUTER_SYSTEM cs JOIN v_R_System rs ON cs.resourceID = rs.resourceID
JOIN v_GS_PC_BIOS gs ON cs.ResourceID = gs.ResourceID

GROUP BY 
cs.Name0,
rs.User_Name0,
rs.User_Domain0,
gs.SerialNumber0 
HAVING COUNT (cs.Name0) > 1
 
what is this code doing wrong and how to I make it work?  

You only need to add the following line:
COUNT(gs.SerialNumber0) AS NumOccurences
 
Whole code:
SELECT 
cs.Name0 AS [Computer Name],
rs.User_Name0 AS [User Name],
rs.User_Domain0 AS [Domain],
gs.SerialNumber0 AS [Serial Number] ,
COUNT(gs.SerialNumber0) AS NumOccurences
FROM v_GS_COMPUTER_SYSTEM cs JOIN v_R_System rs ON cs.resourceID = rs.resourceID
JOIN v_GS_PC_BIOS gs ON cs.ResourceID = gs.ResourceID
GROUP BY 
cs.Name0,
rs.User_Name0,
rs.User_Domain0,
gs.SerialNumber0 
HAVING COUNT (cs.Name0) > 1
 

Thank you.... I ran your code and it only returns 1 row if information.   And we know we have many serial numbers matched up to more than 1 Computer Name.     What else to try?  
 
 

Just to verify - can you run the following query looking for a particular serial number replacing <serial#> with a serial number you know is listed more than once?
 SELECT 
 rs.Name0 AS [Computer Name],
 rs.User_Name0 AS [User Name],
 rs.User_Domain0 AS [Domain],
 gs.SerialNumber0 AS [Serial Number]
FROM
 v_R_System rs
 JOIN v_GS_PC_BIOS gs ON rs.ResourceID = gs.ResourceID
WHERE
 gs.SerialNumber0 = '<Serial#>'
 
 

Yes, when I enter the serial number from my PC it correctly returned my PC's NetBIOS name.
 
 

try this. http://smsug.ca/blogs/garth_jones/archive/2012/09/18/four-reports-to-answer-questions-within-the-reporting-forums.aspx

Thanks but what does ES_DupSerial.exe actually do?   We can't just install 3rd party tools onto our production SCCM servers.  And if this is a SQL report why an .EXE?  
 
Thank you.  
 
 

The setup installs the RDL and reset the data source on the RDL to the CM07/CM12 data source.
 
When you run  the setup, you can grab the RDL from the %temp% directory and cancel the setup, then manually upload the RDL and reset the DS yourself.
 
http://support.enhansoft.com/Blogs/post/How-to-upload-a-report-manually-to-SQL-Server-Reporting-Services-(SSRS).aspx
http://support.enhansoft.com/Blogs/post/How-to-Change-the-SSRS-Datasource.aspx
 
If you have any doubts install it within your lab.