Where do I check my Applecare Expiration Date
Where do I check my Applecare Expiration Date for all of my devices?
iMac, Mac OS X (10.6.7)
http://checkcoverage.apple.com.
This requires entering the device's serial number, and it's case-sensitive. If you don't know where to find the serial number, see Find the serial number of your Apple product - Apple Support.