Need help with strings arrays,remove not the unique elements

Hey all,i have small problem.
I writting small easy PE importing library in delphi and i am faced with problem.
I need to remove all non-unique elements in an array of strings, leaving only the unique. There is a simple solution, but requires additional memory. I do not like it unnecessarily i like a little code.

Code:

 Memo1.Clear;
 //In randomly order for test
 Memo1.Lines.Add('kernel32.dll,ExitProcess');
 Memo1.Lines.Add('user32.dll,FindWindowA');
 Memo1.Lines.Add('kernel32.dll,Beep');
 //There i sort it
 //...
 Memo2.Clear;
 for I:=0 to Memo1.Lines.Count-1 do
 begin
  if StringExists(Memo2.Lines,Memo1.Lines.Strings[I])=false then Memo2.Lines.Add(Memo1.Lines.Strings[I]);
 end;

I also tried a slightly different:

Code:

function Importer_CalculateSize(RealSize:Boolean):Dword; //if RealSize=false then return CountDlls*SizeOf(TImageImportDescriptor)+SizeOf(TImageImportDescriptor)
var
 I,CurrentDllIndex : Dword;
begin
 Result:=SizeOf(TImageImportDescriptor);
 CurrentDllIndex:=0;
 Importer_Sort;
 for I:=0 to ItemsCount-1 do if lstrcmp(PImportItem(Ptr(Dword(Items)+CurrentDllIndex*SizeOf(TImportItem)))^.LibraryName,PImportItem(Ptr(Dword(Items)+I*SizeOf(TImportItem)))^.LibraryName)<>0 then
 begin
  if I+1>MaxItems then CurrentDllIndex:=I else CurrentDllIndex:=I+1;
  Inc(Result,SizeOf(TImageImportDescriptor));
 end;
end;

HAAALP