It Takes my 27inch Core i7 iMac takes 1 minute to boot up?

I've compared the speed to other i7 imacs and their boot time seems to be around 25 seconds. My iMac takes a full minute... I've already used Onyx to clean up and stuff but it didn't affect the boot time. What could be causing this issue and how can I fix it. I bought my iMac January of 2011