-- If you need more information, here is a nice SQL script, which I use from time to time:
DECLARE @TabName varchar(100)

CREATE TABLE #temp (
   TabName varchar(200), IndexName varchar(200), IndexDescr varchar(200), 
   IndexKeys varchar(200), IndexSize int
)

DECLARE cur CURSOR FAST_FORWARD LOCAL FOR
    SELECT name FROM sysobjects WHERE xtype = 'U'

OPEN cur

FETCH NEXT FROM cur INTO @TabName
WHILE @@FETCH_STATUS = 0
    BEGIN
        INSERT INTO #temp (IndexName, IndexDescr, IndexKeys)
        EXEC sp_helpindex @TabName

        UPDATE #temp SET TabName = @TabName WHERE TabName IS NULL

        FETCH NEXT FROM cur INTO @TabName
    END

CLOSE cur
DEALLOCATE cur

DECLARE @ValueCoef int
SELECT @ValueCoef = low FROM Master.dbo.spt_values WHERE number = 1 AND type = N'E'

UPDATE #temp SET IndexSize = 
    ((CAST(sysindexes.used AS bigint) * @ValueCoef)/1024)/1024
        FROM sysobjects INNER JOIN sysindexes ON sysobjects.id = sysindexes.id
            INNER JOIN #temp T ON T.TabName = sysobjects.name AND T.IndexName = sysindexes.name

SELECT * FROM #temp
ORDER BY TabName, IndexName 

DROP TABLE #temp