Windows Black Screen Error is Comman. Infact i had this problem at times this a kind and it occurs due to many Factors.Here are the some fix’s for this problem.
Sometimes it occurs due to Graphical Driver Problem so for this Just Tap on SHIFT button for 5 Times.Then a Window Dailog will popup and Every thing Comes to Normal.
In this fix Use CONTROL+ALT+DELETE Button then it will take you to the Task manager.Now search internet explore.exe and stop the task and start it Again.
By using windows Repair Center.For this restart your PC and as soon as it start Before the windows logo click F5+F6 at the same time then you will be taken to the page with all the system options.Their you can see a option then select Launch Repair.
If non of this works go to Safe Mode and copy all your Important Files from root directory and Setup Windows 7 Again.