Is it safe to upgrade to Windows 10 from a non genuine Windows 7?

Some machines still have the notice to upgrade Windows 7 to Windows 10. (Why you shouldn't upgrade your system is explained below).

The last date for the upgrade for Windows 7 customers was 29th July 2015. However some regions have this date extended till November. After this date very few regions have the upgrade notice visible. Enterprise and Small business will have upgrade option till the end of Lifecyle of Windows 7. Though free upgrade for enterprise machines too have crossed the date.

The notice that you see on the laptop or desktop is basically generated on most of the non-genuine licensed version of Windows. By asking you to upgrade Microsoft will install Windows 10 genuine version on machine. And after finishing the installation, they'll ask for the License key. This has happened for many users who didn't got their machine passed through genuine validation (piracy check).

In short: It is not safe to upgrade if your Windows is not genuine version.

I suggest you to get a DVD of Windows 10 Professional and Install from scratch. Avoid upgrading Windows 7 either by online method or by DVD. The reason being upgrades usually increase the disk size for expansion of new OS. And this results in system performing slower. So by making clean install, you can get assurance that system will not have performance issues. Also do stop the automatic system updates in Windows 10 after installing the OS.