Black screen of death

I recently started watching netflix on my desktop machine (with Silverlight), and after a few days the screen started going totally black. Typing Ctrl-Alt-Del twice has no effect.

This is the sequence of things that appear on the monitor when the machine is turned on:

* The Dell powerup/self-test screen
* Black
* The Windows XP boot screen
* Black for at least 10 seconds
* Dark gray
* The light blue "Windows is starting" screen
* Black
* The light blue screen with user icons for a small fraction of a second. It either turns black before I can click an icon or doesn't appear at all.