If it's a Windows 8 PC then you're already fucked
FTFY
If it's a Windows 8 PC then you're already fucked
If it's a Windows 8 PC then you won't have a product key anywhere on the PC, you have to look for a recovery partition or boot into safe mode.
If it's a Windows 7 PC then what you should do is boot into safe mode and see if you can get to the desktop.
So, today when i came home, i booted up my computer like usual, and booted up windows (i have Ubuntu installed) and its just a blackscreen. I can see my cursor but thats it. Even booting in safe mode gives a blackscreen. For some reason when I start Ubunutu though, everything works fine. Does anyone have a good tool i can use to troubleshoot?