I've tried restarting both by pushing the button and by unplugging the PC. Same result. I get the message that Windows is restarting and then the black screen. I still have a mouse pointer that moves, but that's all...
SFC/ SCANNOW Should do the trick. Had the same problem last winter, but mine came from trying some hacks to my registry. CTRL/ALT/ESC will get you to task manager to get the scan started.