I changed the settings to a later version of Windows XP. If all else fails, you could try to alter the compatibility settings that may be found under Properties by right clicking the RFSim99 icon. This time everything worked and continues to work, as it should. Next, I created a circuit model of my own, saved it and ran a simulation. After unzipping the program for a second or third time, I ran a Sample File from the Open file menu. I encountered both of these quirks when I first installed the application, particularly after I had run my first simulation. Another quirk had to do with plots not appearing after the simulation button was pressed. There were some posts online about how some of the user interface buttons would not appear until hovering the mouse over where the buttons should appear.
This is a very old program and much to the credit of the Gordon Hudson, AD5GG, an extracted version seems to run on Windows 11 in compatibility mode for Windows XP.
Out of curiosity I recently downloaded a copy of RFSim99, authored by Stewart Hyde, to see what it could do and how easy it was to use.
