Motors Vibrate/Hum/ Heat up

Just finished my prusa mendel I3.(I thought). However I loaded sprinter firmware and in pronterface when I try to move the motors they just hum and vibrate and get very hot. I don't want to touch the tuneing on the pololu becuase the motor are hot, so they should be getting enough current. I am useing 6 wire unipolar motors. I have all 5 motors wired as following
A- - A1pin
A+ - A2pin
B- - B1pin
B+ - B2pin

Just for some information, where DO you have the trimpots set? The motors can/will misbehave if they are set too high also, not just when they are too low.

I actually am not really sure. I am going to assume those are the two screw looking things on each driver. However I havent moved them from when they came. I got them from gagets3d

Also the arduino seems to be quite warm under the usb connection.

Are you using the normal A4988 pololu drivers? If so, they each only have 1 trimpot, not 2? The installation instructions said to turn them all the way down (CCW) and then back up I think it was 1/8 of a turn, and then to adjust upwardly from there.

you have the g3d drivers which the bottom one should be closed fully and the top one is v pot i would find out your vref and set your vpot check this link out [reprap.org]