Confusing Electrical Bug-1990 Volvo 740 GL

Hi everybody. I hope someone here will be able to help me out, because I'm at my wits end with my car. I'm having an electrical issue that's causing a lot of problems, and they all pretty much happened simultaneously. As I was driving one day, (regular highway driving, nothing rough or speedy) I suddenly noticed that my A/C wasn't pumping cold air, so figuring I had a minor problem, I tried to roll down my power windows to keep myself cool until I could get home and check it out. Lo and behold, my windows have stopped working, as well as my turn signals. At this point I know I have a slightly worse problem than I thought, so I headed straight home and parked the car. After a quick check of the fuses I discovered that #9 and #21 were blown, so I replaced them and turned the ignition to the accessory position. The fuses immediately blew again. I have checked, disconnected and reconnected everything attached to these circuits, and still have the problem. The only thing I have discovered is that fuse #9 doesn't blow if the headlight switch is off, but the moment I turn them on, it blows. This confuses me a great deal, since I can't find anything on the #9 circuit that is tied into the headlight switch. Any help/suggestions anyone can give me will be greatly appreciated, especially since this is the only car I have, and driving it right now is not only illegal, but during these summer months, is akin to an easy bake oven.