I wrote a function that expands to 64 bits (8x8) that might be usefull...

Create Function fn_BigIntToBinary (@bi BigInt) 

RETURNS Varchar(72)

AS

Begin

/*

-- Returns 64 bits of passed BigInt, each byte separated by a space.

Select dbo.fn_BigIntToBinary(123456789)

*/

 Declare @RetVal Varchar(72), @Hi16a BigInt, @Hi16b Bigint, @Low16a BigInt, @Low16b BigInt,

  @Hi32 BigInt, @RetVal1 VarChar(72)

 Select @Hi32 = @bi / Power(Convert(BigInt,2), 32)

 select  @Hi16a = (@bi / (65536 * 256)) & (Power(2, 16) - 1),

  @Hi16b = (@bi / 65536) & (Power(2, 16) - 1),

  @Low16a = (@bi / 256) & (Power(2, 16) - 1),

  @Low16b = @bi & (Power(2, 16) - 1),

  @RetVal1 = case 

    When @bi > Power(Convert(BigInt,2), 32) then dbo.fn_BigIntToBinary(@Hi32)

    Else '00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000'

      End

 Set @RetVal = Right(@RetVal1, 35)  + ' ' + 

  Right(fn_replinttobitstring(@Hi16a), 8) + ' ' + 

  Right(fn_replinttobitstring(@Hi16b), 8) + ' ' + 

  Right(fn_replinttobitstring(@Low16a), 8) + ' ' + 

  Right(fn_replinttobitstring(@Low16b), 8)

 Return @RetVal

End

Hope it cut&pastes ok....