BattlEye "Windows Kernel modification detected." error

When launching the game I get a "Windows Kernel modification detected." error.

You are either using a cracked version of Windows or you previously installed hack software that disables certain important security features of Windows. Unfortunately, we cannot support systems that run a hacked Windows kernel. To solve this you can try to check your system files for corruptions and possibly repair them by following these guides: http://support.microsoft.com/kb/929833 and http://support.microsoft.com/kb/947821. Otherwise you need to perform a full reinstall of Windows using a legitimate copy.

This answer is copied from BE's FAQ and slightly adapted to be Unturned-specific. Click here to visit the BE support page.