SQL Server 2008: I have 1000 tables, I need to know which tables have data

Try this - gives you the table name and the row count:

SELECT 
    t.NAME AS TableName,
    SUM(p.rows) AS [RowCount]
FROM 
    sys.tables t
INNER JOIN      
    sys.indexes i ON t.OBJECT_ID = i.object_id
INNER JOIN 
    sys.partitions p ON i.object_id = p.OBJECT_ID AND i.index_id = p.index_id
WHERE   
    i.index_id <= 1
GROUP BY 
    t.NAME, i.object_id, i.index_id, i.name 
ORDER BY 
    SUM(p.rows) DESC

It shows all tables and their row counts in a single output.

A simpler syntax:

SELECT  
    [Name] = o.name,
    [RowCount]= SUM(p.row_count)
FROM SYS.DM_DB_PARTITION_STATS p
INNER JOIN SYS.TABLES o ON p.[object_ID] = o.[object_id]
WHERE index_id <= 1 -- Heap or clustered index only
GROUP BY o.name
ORDER BY 2 desc