The only place where you can download Windows 10 safely is directly from Microsoft’s website because Windows is proprietary software. Please download your Windows 10 ISO from Microsoft.
Windows 10 works best with a GPT-formatted hard drive, UEFI mode, and Secure Boot enabled. Please verify all these settings before proceeding with your installation.
You may be correct about your hardware being legacy hardware. Windows 10 requires a CPU with PAE, NX, and SSE2 technologies that Windows 7 does not need. If installing Windows 10 proves impossible, you may have to reinstall Windows 7.