Hello and welcome to justanswer, my name is ***** ***** i will be assisting you today,
I'm sorry about the issue, First press simultaneously the function (Fn) key and the F7 (or F5) key. if that didn't work out try to restore windows 7 os by following the steps below :
1-Click Start > All Programs > Accessories > System Tools program group.
2-Click on the System Restore program icon.
3-Click Next > on the Restore system files and settings window.
4-Choose the restore point that you want to use. You should use the restore point with a date when you still don't have the problem you are facing now.
Let me know the results
Has everything worked out ?