DECLARE @Foo TABLE (Val NVARCHAR(4000))

INSERT @Foo
exec xp_cmdshell N'dir "<dir>" /s /-c /a | find "bytes" | find /v "free"'

SELECT 
   SUM(CAST(LEFT(
            SUBSTRING(Val, PATINDEX('%)%', Val) + 1, LEN(Val))
            ,LEN(SUBSTRING(Val, PATINDEX('%)%', Val) + 1, LEN(Val))) - 5
        )AS BIGINT)) AS TotalBytes
FROM @Foo

USE master
GO
EXEC sp_configure 'show advanced options', 1;
GO
RECONFIGURE;
GO
EXEC sp_configure 'xp_cmdshell', 1;
GO
RECONFIGURE;

EXEC xp_cmdshell 
	N'Powershell -Command "&{$dirs =  	@(		\"C:\Temp\",			\"C:\Tests\"		);		foreach($d in $dirs) 	{$total=0; Get-ChildItem -recurse $d | % { $total += $_.length } ; \"$d   $total\";}}'

EXEC xp_cmdshell 
	N'Powershell -Command "&{$dirs =
	@(
		\"C:\Temp\",	
		\"C:\Tests\"
	);	
	foreach($d in $dirs) 
	{$total=0; Get-ChildItem -recurse $d | % { $total += $_.length } ; \"$d   $total\";}}'