If you jack up the car does the wheel spin freely by hand? If not, remove the tyre and 1) if floating calipers, then unbolt them to swing them out of the way 2) if fixed, then you might need to remove the pads for this exercise. Either way once the caliper can no longer grip the disc, then try spinning the disc. If the caliper was at fault then they should now spin freely. You should also grab the top/bottom of the disc and check to see if there's any wobble in it. If the disc still binds or has free play in it, then it could be your bearings. A caliper can become seized very suddenly although it isn't very common. The above method will quickly enable you to determine where the fault lies.