1. Upgrade to Windows 10 is possible [You don't require license key]
2. We do not have required drivers as of now for Windows 10 in the HP Support Site
3. You might face compatibility issues when it comes peripherals used with the Unit
4. You may have to download required drivers from the manufacturer's website for each hardware component
If you dont like Windows 10 after the upgrade and if you want to switch back to Windows 7, you have to do a clean install using Recovery Media Disks or USB Recovery Media
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