IMPORTANT UPDATE: Microsoft no longer allows upgrade from Windows 7 to Windows 10 with the same Activation Key so please disregard the information below about how it's possible to Activate Windows 10 with the Activation Key of Windows 7. You will need to purchase a Windows Activation Key from Microsoft if you are upgrading from Windows 7. 1TB 3.5'' Desktop HDD Windows 10 Pro Pre-installed for HP Workstation Z820 Z840 Z2 G4 G5 Compatibility: 1TB 3.5'' HDD Windows 10 Pro for HP Workstation Z820 Z840 Z2 G4 G5 Rotation Speed: 7200 RPM Brand: Seagate, Western Digital, Toshiba, Samsung, Hitachi... 1TB Desktop 3.5" Hard Drive HDD with Windows 10 Pro Pre-installed for HP Workstation Z820 Z840 Z2 G4 G5 Note: Images in our listing are stock images. Actual Product that you will receive will be a major brand hard drive. Major brands includes Seagate, Western Digital, Hitachi, Toshiba and Samsung... This Hard Drive is compatible with HP Workstation Z820 Z840 Z2 G4 G5. IMPORTANT NOTE: Windows 10 PRO was installed on this Hard Drive in UEFI Mode. If your System has both UEFI and Legacy Mode, then make sure Boot Mode is set to UEFI mode otherwise your system will not detect the Operating System on this Hard Drive. PLEASE READ BELOW BEFORE MAKING A PURCHASE ACTIVATION: This is a genuine version of Windows - not a pirated 'pre-activated' one. Activation therefore may be required.- If your computer came with Windows 10 PRO pre-installed, then you don't need to do anything. Windows will automatically detect your system's digital license (which is embedded in the hardware) and activate. Your system will also detect the Digital License Key and activate Windows if your computer came with Windows 8 Pro. If your computer came with Windows 7 PRO, then you will need to purchase a Windows 10 PRO Activation Key from Microsoft as Microsoft no longer allows Activation of Windows 10 PRO with a Windows 7 PRO Activation Key. If none of the above situations matches your scenario, then you will need to buy Product Key for Windows 10 Pro. Compatible with HP Workstation Z820 Z840 Z2 G4 G5. No technical knowledge is required. Simply install drive in Desktop, Power it on, let it automatically update devices for your hardware, and you're good to go! Returns: As with all our items we have a 60 day return policy. Item must be in original condition for a full refund. Depending on the item condition upon return, we reserve the right to decide whether to issue a full or partial refund. Shipping: Shipping is via USPS 1st Class Mail or Priority depending on Order Size. While may show you an estimated delivery date, this is not guaranteed as USPS has no guaranteed delivery times for 1st Class Mail. We will ship within 1 business day of purchase, after that we have no control over delivery. If you need your hard drive faster, then choose the Priority mail option. USPS Priority Mail which has 2-3 day delivery times depending how far you are from CA. Product Specifications: Capacity: 1TB Compatible with: Desktop HP Workstation Z820 Z840 Z2 G4 G5. Rotation Speed: 7200 RPM Form Factor: 3.5" Thank you for Watching!!!