The "Purity.dll" file is often re-wrapped with malware that doesn't just affect FL Studio. Modern viruses hide in cracked VSTs to inject keyloggers (stealing your passwords) or ransomware (locking your files). Because Purity is old (32-bit originally), many hackers use it as a trojan horse because security software is less aggressive with "audio files."
To make Purity appear in your instrument list, you must scan for it: How to put Purity in FL Studio after downloading it? Purity Vst Fl Studio 12 Free Download
: Be cautious of unofficial "free" download sites (e.g., from Google Groups or VK), as these often contain pirated content which may include malware or unstable "cracks". 2. Installation Guide The "Purity