Turn the machine off. Unplug the power cord from the wall outlet.
Remove the water tank. Remove the cleaning formula tank. Set both tanks aside.
Remove the screw near the front of the unit, under where the water tank was sitting, using the Phillips screwdriver. This screw holds the front nozzle in place. Remove the front nozzle.
Turn the machine on its side, with the cord side down.
Unscrew the two black screws holding the clear end cap in place, using the Phillips screwdriver. Remove the clear end cap. Remove the single silver screw under the end cap.
Lift up the pivot arm to remove it. Remove the brush belt.
Install the new brush belt over the rollers. Replace the pivot arm. Replace the silver screw to hold the pivot arm in place.
Replace the clear end cap. Replace the two black screws to hold the end cap in place.
Stand the ProHeat unit up. Replace the front nozzle. Replace the screw that holds the front nozzle on.