quick exhaust wiring question. thank you!

quick wiring question?
I just bought and exhaust fan and Im having trouble setting it up. The exhaust fan has 4 wires in it, 2 green , 1 white and 1 black.

I spliced a power cable from a computer cord and it has 1 green, 1 white, and 1 black. There is an extra green wire and Im not sure what to do with it.

1 green wire is just connected to a bolt... and the other green wire is connected to the motor with the other black and white wire.

Sounds like some kind of weird extra ground wire to me. This isn't a computer fan is it? They run on dc power and I'm not knowledable enough about dc to offer advice.

This isn't some huge three phase fan is it?