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== hard drive installation ==The unit is not typically sold with a hard drive. The customer has to obtain a hard drive and install it. The manufacturer recommends using a SATA drive at least 500gb in size or larger. The illustration shows the unit with the hard drive installed. [[File:DVR-C1104SEFDa.jpg]]There are four screw holes on the bottom of the unit case that should be used to secure the hard drive in place. The holes match with those on the bottom of a 3.5" SATA PC hard drive mounting receivers. Solution 2: The manufacturer recommends Seagate SATA drives of 500GB or larger. Make sure you are using a known to be functional SATA drive. The system may not detect the drive if the drive is defective. A defective drive or incompatible drive will not be detected. Another possible cause is a faulty SATA controller on the DVR, which means the DVR would need to be serviced or replaced.Solution 2: The manufacturer recommends Seagate SATA drives of 500GB or larger. It is known to work with the Western Digital WD6400AAKS drive as long as a large enough AC adapter is used. Make sure you are using a known to be functional SATA drive. The system may not detect the drive if the drive is defective. A defective drive or incompatible drive will not be detected. Another possible cause is a faulty SATA controller on the DVR, which means the DVR would need to be serviced or replaced.