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. IMPORTANT NOTE: Windows 10 PRO was installed on this Hard Drive in Legacy Mode. If your System has both UEFI and Legacy Mode, then make sure Boot Mode is set to Legacy mode otherwise your system will not detect the Operating System on this Hard Drive. This listing is for a 1TB Desktop Hard Drive HDD like the one in the images shown. This drive has the Microsoft Windows 10 Professional pre-installed. This hard drive fits most Dell Optiplex models. If you are unsure about compatibility, feel free to send us a message. 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/8.1/8 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. - If your computer came with Windows 7 Pro then will need to enter your 25-digit license key which found on the Windows COA sticker. (This is usually on the case for desktops, and on the base or under the battery for laptops, and printed in the following format: XXXXX-XXXXX-XXXXX-XXXXX-XXXXX). - If you have your own Windows 10 pro/8.1/8/7 product key or are planning to buy one, then these can be activated the same way as above.This drive is in excellent condition and working perfectly. The drive has pre-installed Microsoft Windows 10 Professional 64-bit. If you install the drive and see a "no bootable device" message. Change the BIOS settings to turn off Secure boot and turn on Legacy mode, then restart. This drive does not include the Windows Activation Key. Storage Capacity: 1 TB Drive Interface: Serial ATA (SATA) Form Factor: 3.5" Type: Desktop Hard Disk Drive HDD Returns: As with all our items we have a 60 day return policy. 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.