If you do proceed, take precautions:
The official Cadence site no longer hosts this specific legacy version, but it can be found through trusted academic portals: pspice 9.1 student version free download
Use LTspice if you are on Windows 10/11. It is faster, has no node limits, and is supported by Analog Devices. However, if your professor requires PSpice syntax (.cir files, specific model libraries), then installing version 9.1 (or using OrCAD Lite) is necessary. If you do proceed, take precautions: The official