What was making the noise. Maybe one of your case fans died. When you start the pc, it doesnt show anything on the screen?? Try leaving only the essential components on the pc and start it and see if it works. It might be a psu problem, gfx problem or even ram problem. If these is not the case then the mobo is dead. If you leave the pc on does it do any beeps???
You have bought a crossfire mobo. That means that you can put two identical ATI cards to work as crossfire. Sli is for nvidia gfx cards.