Yes, it is a windows based PC. Before I got to the company, they were shutting down the PLC because they did not know the fault. After I investigated the issue, the VFD had malfunctioned and needed replaced. After replacing it, the fault was able to be cleared. However, the PC itself is fed out of the PLC control cabinet. So, when the PLC disconnect switch is de-energized and power to the PLC was turned off, power to the 4 other PC's also are de-energized....operating software for conveyor systems. Line voltage is fed to the PC's from the PLC control cabinet. The PC is shut down gracefully, but when I tested the receptacle feeding line voltage to the PC after changing out the input card and replacing the VFD after shutting down the power to the PLC control cabinet all together, there was no power to the receptacle as well feeding the PC's....also tracing the circuit to make sure that the 120V circuit going to the receptacle was coming out the control cabinet also. It makes me think that the engineers who wired the PLC wanted to shut down the PC's connected to the PLC also when the PLC was de-energized. My question is...what risk(s) would there be feeding a separate power source to the PC that has control wiring going to the PLC...even when the PLC is de-energized? There must be some reason why it was installed that way, but it doesn't make sense why the PC's would be fed out of the PLC control cabinet as apposed to a 20A / 120V circuit from an electrical panel.