DECLARE @TableName VARCHAR(100)    --For storing values in the cursor

--Cursor to get the name of all user tables from the sysobjects listing
DECLARE tableCursor CURSOR
FOR
select [name]
from dbo.sysobjects
where  OBJECTPROPERTY(id, N'IsUserTable') = 1
FOR READ ONLY

CREATE TABLE #TempTable
(
tableName varchar(100),
numberofRows varchar(100),
reservedSize varchar(50),
dataSize varchar(50),
indexSize varchar(50),
unusedSize varchar(50)
)

OPEN tableCursor
FETCH NEXT FROM tableCursor INTO @TableName

WHILE (@@Fetch_Status >= 0)
BEGIN
INSERT  #TempTable
EXEC sp_spaceused @TableName
FETCH NEXT FROM tableCursor INTO @TableName
END

CLOSE tableCursor
DEALLOCATE tableCursor

--Select all records so we can use the reults, ordered by biggest
SELECT *
FROM #TempTable
ORDER BY CAST(LEFT(dataSize,LEN(dataSize)-3) AS NUMERIC(18,0)) DESC

DROP TABLE #TempTable