Light display working, but not when i log in

When i go to log into windows, i type in my password into my user account, when it first goes into the screen, i see everything fine, i can see all my desktop icons, my background, then all of the sudden the screen goes dark, not 100%, cause i can barely still see things, but really dark. I am on a mac, and have windows installed on it, and the mac side works just fine, light works, i can see everything on the screen, so i know my backlight isnt burnt out or whatever. Any ideas how to reset that setting in windows? My cat sat on my computer and ever since it hasnt worked ha ha