This is a long shot, but I thought I'd ask anyways. I used to have an iMac 24" and the internal hard drive went bad on it. So I bought an external hard drive, installed OS 10.7 on it and booted the computer from that hard drive. I gave it to my friend and he used it for a while with his own external hard drive and I kept mine. It was stolen the other day and he didn't record the serial number. Is there some way I can pull from some file the serial number from the external hard drive that I have in hopes to at least file a police report?
The serial number is read directly from the machine's logic board, so it won't by default be located in any file on the computer.
Did you purchase this computer from an Apple Retail Store? They keep receipts going back many many years in their retail systems and will happily pull a receipt for you if you can prove identity.
Likewise, if you registered the system with Apple upon purchasing (from anywhere) and can call AppleCare, they should be able to provide you with the serial number for your police report. Best of luck!