After installing AMD Ratheon HD 8400 on my Toshiba Satellite C55Dt-A5106 with Windows 10 Home I get a very-but-not-completely dark screen on my laptop monitor only. The dual external monitor seems to be working just fine. How do I fix the laptop monitor? Is it a setting or do I need to reinstall the graphic driver or ??? (I am only a fairly computer literate, and on this Win 10, not so much!) Thanks!