If you are stuck at the screen with the black blinking cursor, you may have a video issue.
First off to disagnose whether you have a hardware issue or a driver issue, you need to get into your computer.
To do this, assuming you are using a laptop, unplug the computer, take the battery out, and then hit the power button a few times. Now plug it back in without the battery and test to see if you can get to the login screen. You can most likely put the battery in at this point also, but you might as well keep it out for now. If you get into the computer, go to teh device manager, and uninstall all video drivers. Reboot and let Windows install a generic video driver. One it boots back up, install the latest driver related to your video card and Motherboard.
If this is a PC, do the same thing with the exception of taking the battery out. Unplug, hit the power to drain the juice from the motherboard, and plug it back in. Hopefully this will get you into your computer.
If after reinstalling the video driver, this happens again, you may have to replace the video card on your computer.
Hope this helps because most of the info I found in this thread seemed quite silly.