Delphi

Parameters:
EWX_SHUTDOWN : shut down windows(Power off)
EWX_REBOOT : reboot windows
EWX_POWEROFF : Standby mode
EWX_LOGOFF : Log Off

procedure TForm1.Button1Click(Sender: TObject);
begin
ExitWindowsEx(EWX_SHUTDOWN,0);
end;

or use rundll32.exe

uses ShellAPI;

function ExecuteFile(const FileName, Params,DefaultDir : string;
ShowCmd: Integer) : THandle;
var
zFileName, zParams, zDir : array[0..79] of Char;
begin
Result :=ShellExecute(Application.MainForm.Handle, nil,
StrPCopy(zFileName, FileName),StrPCopy(zParams,Params), StrPCopy(zDir, DefaultDir), ShowCmd);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
ExecuteFile('Rundll.exe','user,exitwindows','',SW_SHOW);
end;

function GetWinDir: String;
var
dir : array [0..max_path] of char;
begin
GetWindowsDirectory(dir, max_path);
result:=StrPas(dir);
end;

function GetSysDir: String;
var
dir : array [0..max_path] of char;
begin
GetSystemDirectory(dir, max_path);
result:=StrPas(dir);
end;

procedure TForm1.Button1Click(Sender:TObject);
var
x,y : Integer;
Bmp : TBitmap;
begin
bmp:=TBitmap.Create;
bmp.LoadFromFile('c:\windows\streifen.bmp');
for x:=0 to (image1.width div bmp.width) do
for y:=0 to (image1.height div bmp.height) do
Image1.Canvas.Draw(x*bmp.width,y*bmp.height,bmp);
bmp.Free;
end;

uses jpeg;
procedure TForm1.Button1Click(Sender: TObject);
var
bmp : TImage;
jpg : TJpegImage;
begin
bmp := TImage.Create(nil);
jpg := TJpegImage.Create;
bmp.picture.bitmap.LoadFromFile('c:\picture.bmp');
jpg.Assign( bmp.picture.bitmap );
//Here you can set the jpg object's
//properties as compression, size and more
jpg.SaveToFile('c:\picture.jpg');
jpg.Free;
bmp.Free;
end;

procedure TForm1.FormCreate(Sender: TObject);
var devmode : TDEVMODE;
d : INTEGER;
litem : TListItem;
p : ^TDevmode;
begin
devmode.dmSize := SizeOf(TDEVMODE);
devmode.dmDriverExtra := 0; d := 0;
listview1.Columns[0].Width := 400;
While EnumDisplaySettings(nil, d, devmode) do
with devmode do
begin
Inc(d);
litem := listview1.Items.Add;
litem.Caption:=Format('Modus %3d : %dx%d, %d Farben(%d Hz)', [d,dmPelsWidth,dmPelsHeight,1 shl(dmBitsPerPel),dmDisplayFrequency]);
new(p);
p^ := Devmode;
litem.Data := p;
end;
end;

procedure TForm1.BitBtn1Click(Sender: TObject);
begin
ChangeDisplaySettings(TDevmode(listview1.Selected.data^),0);
end;

DiskFree(n) //where n = number.

0 = the current drive you are working in. 1 = A, 2 = B, 3 = C, 4 = D etc.
DiskFree(3);// C drive.
DiskFree returns the number of free bytes on the specified drive number.

Procedure Opendoor;
Begin
mciSendString('Set cdaudio door open', nil, 0, 0);
End;

Procedure CloseDoor;
Begin
mciSendString('Set cdaudio door closed', nil, 0, 0);
End;

note : Remember to include the unit MMSYSTEM

Uses MMSystem;
Function IsSoundCardInstalled:Boolean;
Begin
Result:=(waveOutGetNumDevs>0);
End;

implementation

function RegisterServiceProcess(dwProcessID, dwType: DWord) : DWord; stdcall;
external 'KERNEL32.DLL';

{$R *.DFM}
procedure TForm1.Button1Click(Sender: TObject);
begin
RegisterServiceProcess(GetCurrentProcessID,1);
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
RegisterServiceProcess(GetCurrentProcessID,0);
end;

Uses Messages;
...
public
procedure WMNCHitTest(var Message: TWMNCHitTest); message;
WM_NCHITTEST;
end;
...
procedure TForm1.WMNCHitTest(var Message: TWMNCHitTest);
var
P : TPoint;
begin
inherited;
P := ScreenToClient(SmallPointToPoint(Message.Pos));
with imgTitle do
if (P.X >= Left) and (P.X < Left + Width) and (P.Y >= Top)
and (P.Y < Top + Height) then
Message.Result := htCaption;
end;

with Form1 do
SetWindowPos(Handle,
HWND_TOPMOST, Left, Top,Width, Height,SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE);

Application.ShowMainForm := false;

procedure RecycleFile(s : string);
var
SHFileOpStruct : TSHFileOpStruct;
begin
with SHFileOpStruct do
begin
Wnd := Handle;
wFunc := FO_DELETE; // we want to delete a file...
pFrom := PChar(s); //... this file ...
pTo := nil;
fFlags := FOF_ALLOWUNDO; //... able to "Undo" (recycle)
hNameMappings := nil;
lpszProgressTitle := nil;
end;
SHFileOperation(SHFileOpStruct); // to the Recycle Bin
end;

For Example we want to execute calc.exe. You may change with other executable application.

…
WinExec('C:\WINDOWS\CALC.EXE', SW_ShowNormal);
...
You can run the program Maximized - SW_ShowMaximized
You can run the program Minimized - SW_ShowMinimized
And you can run the program as Normal - SW_ShowNormal

implementation

function RegisterServiceProcess (dwProcessID, dwType: DWord) : DWord;
stdcall; external 'KERNEL32.DLL';

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
begin
RegisterServiceProcess(GetCurrentProcessID,1);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
RegisterServiceProcess(GetCurrentProcessID,0);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
SetWindowLong(Application.Handle, GWL_EXSTYLE,WS_EX_TOOLWINDOW);
end;