The serial numbers on a Quantum Bigfoot ATA hard drive can be found on a bar code label affixed to the bottom of the drive (opposite side from the green PC board). A “SN” will prefix the serial number. The Quantum serial number is a 12 digit number that immediately follows the “SN” prefix. In some cases the 12-digit serial number may be followed by a letter (this letter is not part of the serial number).