Arduino Nano. Is vin also vout?

Development Tools IDE 1.x
2

Hi,

Have a look at this:

https://www.google.co.uk/url?sa=t&source=web&cd=1&ved=0CCoQFjAA&url=http%3A%2F%2Farduino.cc%2Fen%2Fuploads%2FMain%2FArduinoNano30Schematic.pdf&rct=j&q=arduino%20nano%20schematic&ei=hRdSU8S1K8boOqbggTA&usg=AFQjCNHXp_JLeNujR8YC-ofON0-QGBwUNA&sig2=9kgEGE8bJNsdArP3Efoxlw&bvm=bv.65058239,d.ZWU

In particular look at the "5V REG" and "5V AUTO SELECTOR" bits. I can't see how current could be flowing back to the PC. I suspect your PC crash must be due to something else, but I can't explain why the problem stopped when you added that diode.

Paul