My Sims 3 Keeps Minimizing

I have Sims 3 and Sims 3 Pets, I have had it for about a year now. But everytime I am in fullscreen mode, every so often it'll minimize to the desktop.It has done this ever since I got the game. Maybe around every 30 minutes or 15 minutes it does this. However, on desktop mode it NEVER does this. How can I fix this or is it just normal?

I use a Windows 8 laptop.