Something close to this - although not getting desired results
SELECT
dbo.tblComputers.Computername,
dbo.tblSerialnumber.Product,
dbo.tblSerialnumber.ProductID,
dbo.tblSerialnumber.ProductKey,
dbo.tblSerialnumber.Lastchanged,
dbo.tblSerialnumber.SerialID
FROM
dbo.tblComputers
INNER JOIN dbo.tblSerialnumber ON (dbo.tblComputers.Computername = dbo.tblSerialnumber.Computername)
GROUP BY
dbo.tblComputers.Computername,
dbo.tblSerialnumber.Product,
dbo.tblSerialnumber.ProductID,
dbo.tblSerialnumber.ProductKey,
dbo.tblSerialnumber.Lastchanged,
dbo.tblSerialnumber.SerialID
HAVING
dbo.tblSerialnumber.Product = Like 'Microsoft Windows Server %200%'