本例效果图:

代码文件:
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
uses PsAPI; {GetModuleFileNameEx 函数需要它}
{根据窗口句柄获取所在程序路径的函数}
function GetProcessExePath(h: HWND): string;
var
pid: Cardinal;
pHandle: THandle;
buf: array[0..MAX_PATH] of Char;
begin
{先获取进程 ID}
GetWindowThreadProcessId(h, @pid);
{再获取进程句柄}
pHandle := OpenProcess(PROCESS_ALL_ACCESS, False, pid);
{获取进程路径}
GetModuleFileNameEx(pHandle, 0, buf, Length(buf));
CloseHandle(pHandle);
Result := buf;
end;
{测试当前程序}
procedure TForm1.Button1Click(Sender: TObject);
var
path: string;
begin
path := GetProcessExePath(Handle);
ShowMessage(path);
end;
{测试记事本 - 需要随便打开一个记事本}
procedure TForm1.Button2Click(Sender: TObject);
var
wh: HWND;
path: string;
begin
wh := FindWindow('Notepad', nil);
path := GetProcessExePath(wh);
ShowMessage(path);
end;
end.
窗体文件:
object Form1: TForm1
Left = 0
Top = 0
Caption = 'Form1'
ClientHeight = 116
ClientWidth = 471
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'Tahoma'
Font.Style = []
OldCreateOrder = False
Position = poDesktopCenter
PixelsPerInch = 96
TextHeight = 13
object Button1: TButton
Left = 112
Top = 33
Width = 233
Height = 25
Caption = 'Button1'
TabOrder = 0
OnClick = Button1Click
end
object Button2: TButton
Left = 112
Top = 64
Width = 233
Height = 25
Caption = 'Button2'
TabOrder = 1
OnClick = Button2Click
end
end