Black screen with blinking cursor

more details to the problem would help like when the situation happens. From what you provided, it may indicate that your system is not booting up. Attempt to boot in safe mode and last known-good config. Both options can be found by tapping F8 every 2 to 3 seconds while the computer restarts to get to the advanced options screen of Windows. You can then try Last Known-Good Config and Safe Mode and see if either one will work for you,

This things generally happen when explorer.exe is missing in the task manager ..
at that time u just press alt+ctrl+del
file>new tasks>explorer.exe
then it work fine!!!!