I get three beeps on iMac.

Hello Judy, good morning,

This 3 beeps are related to problem with your Ram as far as I know, it's like the blue screen before Bios on the windows.

either you are extremely unlock and the ram barrets came faulty either you could try some technics bellow: open the ram socket if you are not unlucky enough to had taken one of the latest 21" (if you can't access the ram than go see bellow for doing a NVRAM/PRAM reset, it's about the only thing you could try as far my knowledge ) that doesn't come with quick ram access, if you have the old or a 27" recent than proceed, try first pushing depper the ram inside its sockets, be gentle those computers aren't fragile but everything can happen go with love... After presing the barrets deper try to start if the same error happen try now switching places, take them out and inverse places try again, if again not try starting only with one to check if one got mad, if this again failed and you didn't solve, try doing a NVRAM/PRAM reset (easy to do ) link

If everything fails you would need a knowing working compatible ram and test if it than fails could be the Mother board is faulty and than... We'll how to say.. You dooomed