pc based led blinking

guys,
I want to make a very simple project in which I can switch off/on led with my pc keyboard. I have a good knowledge about mc. So anybody plz help me, where to start from and plz don't suggest me using vb6 coz i wanna make it using interrupts and through serial port programming???

thanks

It's easy enough to use a terminal or C to send data through a serial port on a computer. Then using UART receive interrupts on the mc process the data so if gives you the desired result. What part are you having trouble with? If you have a good knowledge of mc, you're halfway there.