Instead of a raw ISO, security professionals often use pre-configured virtual environments designed for vulnerability research: End Of Windows 7 & What It Means For You - Cantium Insights
Perhaps the most important warning: from untrusted sources. These images are frequently bundled with malware, backdoors, registry modifications, and other "gifts" that compromise your system immediately upon installation. Even if the ISO appears to function normally, it may be silently exfiltrating data or providing remote access to attackers.
Many corporate, industrial, and medical networks still run legacy software that only works on Windows 7. Penetration testers use these environments to replicate client infrastructure and find potential attack paths without disrupting live systems.