Which is the best to purchase Windows 10 PRO OEM or FULL RETAIL PACK?

Full version (Retail):

- Includes transfer rights to another computer.

- Can change the motherboard

- 90 days of technical support

- Doesn't require a previous qualifying version of Windows.

- Expensive

OEM System Builder version:

OEM versions of Windows 10 are identical to Full License Retail versions except for the following:

- OEM versions do not offer any free Microsoft direct support from Microsoft support personnel

- OEM licenses are tied to the very first computer you install and activate it on

- OEM versions allow all hardware upgrades except for an upgrade to a different model motherboard

- OEM versions cannot be used to directly upgrade from an older Windows operating system

You can reinstall and reactivate Windows 10 either full retail or OEM System Builder as many times as you like on the same computer. 

When you upgraded from a previous version of Windows or receive a new computer preinstalled with Windows 10, what happened is the hardware (your PC) will get a digital entitlement, where a unique signature of the computer will be stored on Microsoft Activation Servers. The Windows 7 or Windows 8 genuine license you were previously running will be exchanged for a diagnostics key.

Anytime you need to reinstall Windows 10 on that machine, just proceed to reinstall Windows 10. It will automatically reactivate.

There is no need to know or get a new key, but if you have issues with Digital Licensing or the Activation Troubleshooter, you can utilize an existing Windows 7 or Windows 8/8.1 product key you already ownto reactivate if necessary. or use the reset function in Windows 10.

If you are prompted to enter a product key, click 'I don't have a key' and 'Do this later'