Alternator Problem

[Slipper]

Having issues with what i think is my alternator. Whenever the car is running at idle and i do anything electrical related (power windows up/down) and say hold it down the headlights dim and the car appears to drop in revs and labour somewhat, when i 'overload' the system (hold all 4 power window switches down) it dims consderable and from inside the engine bay i can hear a crack or a clicking sound, but whats interesting is after overloading it once or twice its gone, but the back again a few seconds later when i press something. Battery was replaced just over 1 year ago but has since gone flat twice for reasons unknown to me, does anyone have any ideas what it could be? is it indiciative of a dying alternator???
FYI no speakers/woofers/anything other than stock which could be overloading the amps

Thanks

[RiCeY]

Check battery voltage when the car is running, should be over 14.0v. If its less the alternator probably isnt charging.

Any aftermarket accessories fitted that could be causing current draw when the car is off?