[PhoeniX]

ммм... возможно, сейчас посмотрю, мб будет работать...
это?

Код:

function AttachToFile(const AFileName: string; MemoryStream: TMemoryStream): Boolean;
var 
  aStream: TFileStream; 
  iSize: Integer; 
begin 
  Result := False; 
  if not FileExists(AFileName) then 
    Exit; 
  try 
    aStream := TFileStream.Create(AFileName, fmOpenWrite or fmShareDenyWrite); 
    MemoryStream.Seek(0, soFromBeginning); 
    aStream.Seek(0, soFromEnd); 
    aStream.CopyFrom(MemoryStream, 0); 
    iSize := MemoryStream.Size + SizeOf(Integer); 
    aStream.Write(iSize, SizeOf(iSize)); 
  finally 
    aStream.Free; 
  end; 
  Result := True; 
end; 

function LoadFromFile(const AFileName: string; MemoryStream: TMemoryStream): Boolean; 
var 
  aStream: TFileStream; 
  iSize: Integer; 
begin
  Result := False; 
  if not FileExists(AFileName) then 
    Exit; 
  try 
    aStream := TFileStream.Create(AFileName, fmOpenRead or fmShareDenyWrite); 
    aStream.Seek(-SizeOf(Integer), soFromEnd); 
    aStream.Read(iSize, SizeOf(iSize)); 
    if iSize > aStream.Size then 
    begin 
      aStream.Free; 
      Exit; 
    end; 
    aStream.Seek(-iSize, soFromEnd); 
    MemoryStream.SetSize(iSize - SizeOf(Integer)); 
    MemoryStream.CopyFrom(aStream, iSize - SizeOf(iSize)); 
    MemoryStream.Seek(0, soFromBeginning); 
  finally 
    aStream.Free; 
  end; 
  Result := True; 
end;