I recently bought an iMac at a garage sale. The seller thought it was dead, but it turned on just fine, so I'm going to enjoy it while it lasts. I'm not familiar with Mac OS commands and want to find out as much information as I can about the iMac before I can no longer fight the urge to crack it open. How do I look up which logic board I have through the OS? I have 10.4. Thanks in advance.