Several users recommend various circuit simulator software for Windows, including Qucs, MultiSim, and Eagle, with MultiSim offering a trial version. PSpice is highlighted for its effectiveness, especially the free student version, while SPICE is noted as the best for analog circuits. EDA tools and open-source options like Logisim and klogic are also mentioned for digital circuit simulation. Ngspice is suggested for mixed circuit simulations. LTSpice is another recommended option for users seeking circuit simulation software.