Hello - My iMac, 20 inch early 2008 won't start up. When the power button is pressed i get the start up chime, the fans...

Is it a bluetooth keyboard? - first remember that the keyboard needs to be turned on. You need to pair it using the pin number issued by the iPad when it recognises it... You need to provide a bit more information about what you are trying to do and what error messages you are getting..