If you are using an earlier Windows version like Windows 7 not updated with all security patches (at least from March 2015), the installation of NoMachine (client or server) v. 6 will complete with errors related to NoMachine drivers. Everything except USB forwarding, Disk sharing and microphone will operate correctly.

Nevertheless, we strongly advise to keep your system up-to-date.

NoMachine drivers v. 6 are doubled signed with Microsoft SHA-256 signature (primary signature) and SHA1 (secondary signature).  Windows 7 supports SHA-256 signatures but it requires updates, please see: https://technet.microsoft.com/en-us/library/security/3033929

Such update can be downloaded at: https://www.microsoft.com/en-us/download/details.aspx?id=46148