Left-hand and right-hand are referenced from the point of view of the tractor operator.
The flat backside of the belt rides on flat idlers; the inside vee rides in v-idlers and pulleys.
The electric PTO clutch must be removed to replace the drive belt. Loop the belt around the engine pulley and v-idler and within the belt guides (#1, blue). When re-installing the clutch be sure to engage the anti-rotation bracket into the base (#1, red).
The belt guide for the middle v-idler pulley must be removed. Note how the guide post fits into a bracket on the frame (#2, blue). Remove belt from pulley.
The idler tensioning spring attaches to the idler arm and the frame (#3, white).
Pull the left-hand run of the belt onto the middle flat idler (#4).
Poulan PRGT25H48 mower deck belts (#5).