1992 Lexus ES 300 Electrical and cam noise

when I'm driving in the daytime the car runs fine. at night when i use my lights the car loses power and the battery drains. simultaneously the head lights gets low. when turning the head lights on, the radio turns off. the A/C will not come on at all. the front side passenger window will not rotate up or down. the front dash speedometer, gas indicator, temp gauge, RPM indicator, Battery indicator will not work. it appears as if the alternator is not working or not working properly. the car will run until the battery gets low. it runs fine other than what i have explained. i want to know what is causing the problem, if it can be fixed and how much it will cost. i just purchased the car and i feel i buy a lemon


[img:1f046eb9cf]http://www.2carpros.com/forum/automotive_pictures/415173_800px3rd_Lexus_ES300_2.jpg[/img:1f046eb9cf]