Zmodo offers DVR's with or without hard drive installed. If you are looking to customize or replace a new drive inside your Zmodo DVR, we have all models in stock. The standard drive is SATA 3.5 inch for Zmodo brand DVR's. Our hard drives are guaranteed to work with any model Zmodo brand system. Zmodo currently does not offer 2TB drives in 4, 8 or 16 channel systems. You can purchase any DVR without drive and add one if these retail box Western Digital Green drives and have the power of long time recording.