there is no way your computer is making noise. the noise you hear in the old pentium one computers, is the hard drive searching.. ecu has no hard drive.
if you hear your starter click, but not crank then you have a power/ground problem or a short in the starter. the main relay does not control cranking, only the fuel system. if you have a starter kill or an ignition kill on your alarm then i would say yank that bitch out and put it back to stock (if it is not stock). and next time it doesnt do it, check for spark real fast. sometimes the coil/ignitor goes out or becomes intermittent. also check for fuel next time it happens.