I am creating a not so big application and I want to give the users a context-sensitive help without creating a big windows helpsystem or using all kind of tools

Most of the times it’s overkill to use tools to create a real Windows-Helpsystem for smaller applications. However, often you’d like to give the user some help besides a printed manual.
Here is a small example of the way I do it:

Create a new application with 2 forms. The second form will be the Help-form in this example. On the second form is a RichEdit-control called “RedHelp” with the ReadOnly-property on True and the OnKeyUp-event of  RedHelp is implemented as follows:

procedure TForm2.redHelpKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
  if key = VK_ESCAPE then close;
end;

For the first form I set the KeyPreview-property on True and I placed three components on the form as example.
Of course there are other ways and more sofisticated ways to do this, but I wanted to keep it simple.
The complete code of Unit1 is here below:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Memo1: TMemo;
    RadioGroup1: TRadioGroup;
    procedure FormKeyUp(Sender: TObject; var Key: Word;
      Shift: TShiftState);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

uses Unit2;

{$R *.DFM}

procedure TForm1.FormKeyUp(Sender: TObject; var Key: Word;
  Shift: TShiftState);
var dir, s, HelpFile : string;
begin
  if key = VK_F1 then                                       //if a F1 is pressed
  begin
    s := Form1.ActiveControl.Name;                //look which control is active
    if s = '' then                //when e.g. an item off a RadioGroup is active
      s := Form1.ActiveControl.Parent.Name;
    if s = '' then s := Application.ExeName;              //always get something

    dir := ExtractFilePath(Application.ExeName);//get the applications-directory
    HelpFile := format('%s%s.rtf',[dir, s]);        //make the complete filename
    if FileExists(HelpFile) then                       //if it's exists, load it
    begin
      Form2.redHelp.Lines.LoadFromFile(HelpFile);
      Form2.Show;
    end else                                      //if it's not there, create it
    begin
      Form2.redHelp.Lines.Clear;
      Form2.redHelp.Lines.Add(format('Help for %s-control', [s]));
      Form2.redHelp.Lines.Add('Add your helptext here');
      Form2.redHelp.Lines.SaveToFile(HelpFile);
    end;
  end;
end;

end.