Does it matter where you ground a vmod? I was thinking I'd just put the vmod into a fan header and plug it into the motherboard - is this better or worse than any other method, or does it not make a difference?
Get a multimeter, and turn it to the diode symbol. Put a probe on a known ground (case if the board is screwed in), and test it against your pin you think is ground. if the digital readout says anything close to 000, then you found a ground.