I'm an I7 6700HQ CPU 2.60ghz with 16gb ram My graphics card is an Nvidia geoforce gtx960m with 4gm vid ram, So this machine more than meets SL's min requirements. I'm sure this is a setting I need to change, but have no idea where to begin. I've included a picture of the effect. It strobes to black and then regular picture quickly, with prims blinking in and out. I appreciate the suggestion, but updating didn't work, so I added a second picture, as the problem is not solved. !!!! Thank you. What worked was selecting the Nvidia chip set as my preferred graphics processor!! I was not aware I even had to do that. Not only did it work, but SL automatically selected ULTRA as my basic setting, and things are running amazingly fast. THANK YOU.