Black screen with blinking cursor!! help!

Hi there my Windows Vista laptop was working fine before, and now when I try and start it up, it goes straight to a black screen with a blining cursor/underscore in the top left corner.
I've tried the ctrl-alt-delete thing, which doesnt take me anywhere but the startup place again,
the only button I can press is the ESC button,
I've done the shift 5 times, that does nothing at all, no sounds or anything
And I can't press f2 or anything to get to safe mode.
HELP PLEASE