DVI output only working on Windows, not during booting or on Linux

DVI output only working on Windows, not during booting or on Linux

So yesterday I booted my laptop up and the external monitor I have it connected to just stayed black. At first, I thought the problem would go away when Ubuntu was loaded, but it didn't. I tried to reboot a few times, to no avail. Then I decided to give Windows 7 a try, and suddenly (at the login-screen), my external monitor turned on and worked like normal.