-- Try to use this FUNCTION instead of any temptables, looping, dinamyc SQL and so on.

if exists (select * from dbo.sysobjects where name = 'f_hextostr' and xtype = 'FN')

drop function [dbo].[f_hextostr]

GO

CREATE FUNCTION [dbo].[f_hextostr] (@hexstring VARCHAR(512))

RETURNS VARCHAR(256)

AS

begin

 declare @char1 char(1), @char2 char(1), @strlen int, @currpos int, @result varchar(256)

 set @strlen=len(@hexstring)

 set @currpos=1

 set @result=''

 while @currpos<@strlen

  begin

   set @char1=substring(@hexstring,@currpos,1)

   set @char2=substring(@hexstring,@currpos+1,1)

   if (@char1 between '0' and '9' or @char1 between 'A' and 'F')

    and (@char2 between '0' and '9' or @char2 between 'A' and 'F')

    set @result=@result+

     char((ascii(@char1)-case when @char1 between '0' and '9' then 48 else 55 end)*16+

     ascii(@char2)-case when @char2 between '0' and '9' then 48 else 55 end)

   set @currpos = @currpos+2

  end

 return @result

end

GO

-- After filling rows of Your example, do simple this:

update #HexToAlpha set alphastring=dbo.f_hextostr(hexstring)

Best Regards: Richard