Honor the legacy of the Pro-53 by making music—not by risking your computer’s security. Download one of the free synths mentioned above, and you’ll have that warm, vintage analog sound back in your tracks within minutes. Legally, safely, and with a clean conscience.
If you specifically want that classic Prophet-5 sound, — it's vastly superior to the old Pro-53 in every way. For now, start with Tyrell N6 (free) which offers fantastic analog character. Native Instruments Pro 53 Vst Free Download