Just had this problem with my granddaughter’s 3year old Mesh. The psu could provide enough power to install and run XP but trying to take more power to install another program caused a restart. New PSU cured the problem.
its the bit the mains cable plugs into, usually held in place by 3/4 screws and has a loom which provides power to all your components, looks like click here takes about 10 mins to swap, make sure its set to 240 volt not 110, take time to remember which leads went where, check and recheck all connections and your done. check the wattage of your old psu and make sure you get a higher one