Don't use the H50 cooler it's really not very good, but it shouldn't be that bad.
Firstly, has he installed the sink correctly to the CPU? Used thermal paste? Applied i properly? He might need to reseat it.
Second, the H50's fan must be used as an INTAKE - i.e. drawing cool air from outside the case over the radiator - to work properly. This means you give up one of your 120mm fans as an exhaust.
Thirdly, what's your CPU? Is it overclocked? If it's an i7 then they run too hot for a single 120mm radiator to handle properly.
Basically, no case is going to aid that cooler.
Try reseating the cooler: clean off all existing thermal paste and re-applying it (instructions for best approach for your CPU can be found online) then put the unit on. Make sure the fan is intake.