I saw this awesome control panel and i want to make one. I want to know how can i do the folowing.
Using arduino, when i press a button, i would like my pc to open a program. Lets say notepad.exe just for the sake of keeping it simple.
What would be the right way to do that? How can my pc pick up the command coming from arduino and execute it?
This involves running a program in Windows, not just an Arduino programming.
Are you able to program for Windows?
This is something I have no experience in.
I would start with deciding how the two will connect (presume USB) and how to read the data sent from Arduino. Decide on the data to be sent and how to interpret it. Then program accordingly.
You could get a Leonardo or an Esplora or a DFRobot Beetle and use their "native" capabilities as HIDs (as keyboard, mouse).
I think that there are a couple of ways to program a Uno's 16U2/8U2 as a keyboard or mouse, too.
You can program the PC in any language that can communicate with the Arduino over a serial connection.
This Python - Arduino demo might give you some ideas. The same approach should be applicable for any language. I think the Python code will work on Windows if you put in the correct COM port reference.
That link also has a JRuby version that uses the JVC.
The general idea is that the PC program listens continuously for messages from the Arduino and then causes other stuff to happen on the PC depending on what the message contains.
You mentioned "notepad" in your Original Post. If your idea is that the Arduino can cause a PC program to start and can then interact with that program things will probably be a lot more complicated - mainly because the "listening" PC program will already be using the COM port.
You might be able to do something like that using an Arduino that can appear as a keyboard - if you can do what you want with a regular keyboard.
It would be best if you describe in more detail what you hope to achieve.
Open Start Menu>notepad(right click)>Properties
Click on Shortcut Key and then press a shortcut key that is not used for anything else
Program a sketch for an Arduino that can use the Keyboard library that sends that shortcut key when the button is pressed.
This is a pretty simple solution that should work for opening most any application and any other action that can be triggered by a shortcut key. If you need to accomplish actions that aren't already controllable with a shortcut key you might want to check out EventGhost. If you need to control your computer from a greater distance than USB will easily allow then you can also send commands to EventGhost through a network using Ethernet or WiFi.