Sony VAIO goes black after start-up

Hello,

My Sony VAIO Windows 7 latop seems to boot up fine. The screen goes black after the "welcome" screen. It starts up in safe mode and the screen works fine. But when trying to start normally, this problem appears. I have tried taking out the battery and booting up just with power but the same problem occurs. This happened after working with it remotely, coming back to my office and starting it up again. Again, everything seems fine right up to the point where my desktop normally appears. Sometimes the desktop flashes up then immediately goes black with no mouse pointer. Any ideas?