sounds like either one of the callipers is seized or maybe just the pad seized into its carrier in which case you may be able to remove the pads clean up & put copper grease on them,do both sides.you will need to find out which wheel is getting hot/binding to find out where the fault is check it after couple of mls,you may have to jack it up & spin the wheels.you say the pedal is hard if you cant find which wheel is binding then get it looked at by a mechanic as the person above said you dont want to mess with brakes.