I am using PIC 16f877A I am using serial communication using PIC
when i press switch on PIC i want a file like music to turn ON on my pc,
can i do it using PC.
Yes you can but you need software on the PIC to send the command and software on the PC to interpret it and perform the action you want. The PIC cannot make the music play directly. You need a link between them too of course, either RS232 if your PC has a standard serial port or USB otherwise.
It is really a software challenge, the hardware is fairly simlple.