A clients computer that I was working on had a weird problem where once the computer screen would become black right after the Windows Loading Logo finishes. In other words, once you enter the login screen or load up windows the screen will go black.

The first test you should do is to boot into safe mode. To do so, turn on the computer and repeatedly hit the F8 key and choose Safe Mode. Once done, boot into safe mode and if it displays correctly that means it is most likely a bad driver installed for your display adapter. In safe mode uninstall the driver currently being used for your display adapter then restart the computer. Now find the correct drivers for your video adapter online, download it, and then install it.