Every manufacturer (Samsung, Sanyo, Sony. Hitachi, Philips etc..) use different IR code to communicate with IR devices. For an example :- Receiver determines that you pressed "Power" button by identifying the control as 0001 and "Vol +" 0010. That code contains with binary numbers (it have simply 1 and 0 :) ).
Controlling PC with an IR remote
You can make a simple serial port IR receiver to receive signals from any IR consumer remote control and learn various signals from many remote controllers. After you learned IR signals from your remote control, you can define what should happen when you press Power button on your remote. You can set up your remote controller to start a window or play songs or even mouse movement ( Your IR remote controller as an IR mouse). (Or you can buy remote with its receiver that comes with Windows XP Media Centre Edition 2005 by making Microsoft rich)
IR receiver for serial port (Circuit Diagram)
Software configuration for your Circuit
Using serial port IR receiver you can make and collect IR codes for you own Universal IR Remote controller data base. You can Backup and Restore (Receive and Transmit) IR codes from your remote controller. If you cannot find your remote controller in the future you can get that IR code to make a remote controller using PIC.
Make a Programmable Universal IR Remote Controller with your IR Receiver
How to configure your circuit with winLIRC