FIX FOR WINDOWS 7
Click the start button on the bottom left of your screen
Type %appdata% and hit enter
Click the roaming folder, and then hit the appdata folder while in windows explorer (click the folder before that one in the file path)
Hit the letter "s" on your keyboard
look around that area of folders that start with s, until you find "ShopSim"
Open it
Open the save games folder
in there there should be a "settings" file
right click and delete it
Relaunch the game
Everything should be working fine. I have not found a way to use fullscreen, so i use windowed mode and stretch the tab so that ift covers my whole screen, i hope this works for you guys