Go into "safe mode" (when booting up press the "F8" key,, this will bring up a page where you select the "safe mode" option. From here the computer screen will look black with white text going upwards, wait a few seconds/minutes (depending on your computer hardware), when you are in, go to "add and remove". You will need to delete anything that is related to your monitor and video card (IE: nvidia, XFX, ATI) and of coarse the monitor drivers IE. hp, sony etc. When deleted reboot your computer, you will see something like "found new hardware" or similar. Just re-install the drivers that relate to hardware on board your system.
Please post back if you have any more problems or questions.