If it's spinning and the LED flashes but it issues errors, well I'd suggest other things. Like removing the cable, check the pinouts for continuity. Clean all the connections at both ends. Try a disk head cleaner. Barrow another drive from someone else if possible and isolate the problem.
Booting drive B is not normal, it's a hack. Since you are getting activity and errors it's not going to solve anything. Best thing to do is replace/repair the internal drive mech and carry on.
