MIDI to USB adapter with Arduino?

I am trying to turn my Wii drum kit, which has MIDI out, into a digital drum kit. I don't have a MIDI to USB adaptor, and I don't plan on buying one. What I want to do is set up the rx/tx on midi to analog in on Arduino, then relay that through USB to my desktop where I will use these MIDI signals to trigger drum hits in a program I am using. Any ideas?

Thanks!

Can you explain what you mean by this please:-

What I want to do is set up the rx/tx on midi to analog in on Arduino,

http://arduino.cc/en/Hacking/MidiWith8U2Firmware