Windows Vista boots to black screen without a mouse cursor

[Saussure]

Yesterday, when starting my computer, after the computer had displayed the usual splash screen with the brands and makes and the animated Microsoft bar, it booted to the password screen, but the screen remained black throughout this process, without a mouse cursor. I only knew, or guessed, that it had reached the password screen because the loudspeakers were turned on and it made that usual welcome sound.
So I did a hard shutdown by pressing the power button for a few seconds. Then I restarted the computer, was told that it had not been shut down properly and was given a choice of how I wanted to start Windows, so I chose to start Windows in normal mode, and everything proceeded smoothly from there.

Now, day before yesterday, the same thing (black screen) had happened (black screen without a mouse cursor), but the loudspeakers were on mute, so I don't know where in the booting process it had reached or if it played any sound at all, so I did a hard shutdown, and restarted the computer. It booted normally (without telling me that it had not been shut down properly), took me to the password screen etc., loaded normally, ran smoothly.

What is wrong? My Sony-Vaio laptop is two years old. It has Windows Vista Home Premium SP1, 2 GB of RAM, with the latest patches and Windows Updates. Security Software is Norton Internet Security 2010, latest build and updates. I do not have a Vista CD, by the way - Vista came preinstalled.

[jazz836062]

Check device manager to see if there are any "Unrecognized" devices. This can cause vista to take a really long time to boot. Also try doing a start-up repair, see here.