Windows 8 has some compatibilty issues with some programs, especially avast, and driver pack solution, so if one day you restart your machine and it takes you to a black screen after log in , just press control+shit+esc key, it will bring up task manager, then on the bottom left corner, click on more details, then go to file on the top left corner and click on it, then Run new task, and type in "explorer" and then enter, if you do this twice, it will take you to the desktop, the blackness goes away, however sometimes it doesn't, so on the run button where yu typed in "explorer" type in "appwiz.cpl", this will bring up the windows uninstall blah blah and then go where avast is or drp or any program that you recently installed , then uninstall it, alternatively you can type in "rstrui.exe" this will bring up system restore, then choose a restore point that will work and thats all