second screen always shown after installing windows 8

Hi everyone,
I installed windows 8 on an Acer aspire 8320TG with AMD HD 6370 graphics card. This laptop is according to Acer not suitable for windows 8 but it worked...
However, my screen is extended to the right and I can't switch this off. Since I don't have a second monitor I only notice this when my mouse sometimes gets lost or when I make a screenshot. I tried changing some settings in the "screen resolution" dialogue, without success. Am I just not finding the right settings for that or is it some compatibility-issue?

thanks
David

Try Start P

oh nice I didn't know about this menu. It works.
Although it first only showed me a black screen and I had to restart to see anything again. But now everthing is good.

Good