My PC keeps failing to boot, the screen runs up to giving boot window with three dashes running across beneath the window writing.Then it stops ,giving a screen with several selections one of them allows the screen to boot after a period has expired allowing this to run until time expires. Leaves my display with a no signal present on monitor screen.I have tried to run my Xp disc but this auto brings up windows setup screen.Unable to activate any of the options as keyboard is not active. I have to turn off the computer to allow any further interaction with keyboard. The cycle as explained repeats itself.I do not know whether I have a hardware fault or software fault.

I have had this problem with Vista. I had to rebuild my computer with the disk.

In order to do this I booted in safe mode (safe mode should be an option on the screen with the countdown)
And backed up my pics, music, and movies to an external drive.
Then I just ran my recovery disk.

There may be other ways, but this is an option if you have the disk.

Hope it helps..