Windows 7 wouldn't start, stuck in black screen

The other day my laptop would not start. It got to the black screen and would go no farther. I tried starting 2 or 3 times and gave up on a normal start. I put an Acronis boot disc in and it started. It has started successfully several times since then and it's running OK. In fact this post is coming from my laptop. Does anyone have any ideas what caused this to happen?