I have a pavillion pc the fans work but it will

Fans meaning CPU and Power Supply and Chassis? Try taking out your Ram and see if you get a beep code. If you do that's good, put it back and take out your video card, again for beep code. If you have internal video, during boot up try a combination of keys which used to get you to BIOS? Can't? Try putting in an external video card. Do you get a screen? If not, it could be your processor, although we really haven't ruled out your Video yet. Does your keyboard flash when you turn on? Try holding down a key for about 30 sec. while booting and wait for a beep. You should go into BIOS.