I was on an sim IFR flight (Flight Sim 2004 with flight plan created) from Chicago Midway to Louisville, KY. Flying the Mooney blue and white. Using Real Weather, updated every 15 minutes, flying at 11,000 feet.About 20 minutes outside of Chicago the wx started to deteriorate. A long line of dark storm clouds was forming to my front. I could also see lighting cloud to cloud and cloud to ground. What to do? In real life a no brainer. Give the storm wide berth, no question about it. Or do a 180.But in the sim that would mean disengaging the GPS, and steering around the storm and I don't think FS2004 allows you to restart the flight plan using GPS/NAV after missing several check points. Of course I could have just turned off the GPS, navigated around the storm manually and then got back to the original flight path and flew on into Louisville manually. (Using the GPS display)What would you have done?All of a sudden the cockpit was immersed in a solid dark gray color with light to moderate turbulence. The ground was not visible. (nor anything else.) I could still see the aircraft identifier little thingies, (showing type, altitude, distance) of other aircraft in the area, but that's all I could see. I cancelled the flight plan, contacted Indianapolis and landed at Indianapolis International. As I decreased the altitude I must have come out of the storm because I began to see shapes of clouds when reflected by lighting and every once in awhile, I could see the ground, but not well. It was definitely an ILS approach and landing all the way. Funny thing, not one drop of rain, thoughRegards,Don S

Preflight - weather brief maybe....