Finding a safe source for downloading Windows 7 can be tricky now that official support has ended. Since you have an original product key, your best bet is to look for copies that were available through Microsoft, such as the Digital River downloads, but these are difficult to come by officially now. If you bought the retail version, you might have access to legitimate media through the retailer you purchased from, or by borrowing an installation disc from a trustworthy source.
As for security, using Windows 7 comes with risks since there are no more security updates. It's crucial to have good antivirus software and a robust firewall. Consider running the OS in a virtual machine for added security. Also, limiting internet use and avoiding sensitive tasks can reduce risks. Switching to a supported OS for web browsing or tasks involving personal data might be worth considering.
Lastly, avoid downloading from unofficial sites to prevent exposure to malware. If feasible, you might also consider upgrading to a newer version of Windows or dual-booting with a more current OS for comprehensive security. If you're interested, you might look into extended security updates that could still be available for enterprise customers through certain vendors.
