Vista - start up/boot problems

I have a Sony Vaio computer that is awesome and it's running vista.
so the problem is that when ever i hit the power button the computer sleeps
which is good because i can come back to it later and everything loads up
correctly.
the bad part is that when ever i power down from the start menu and later,
turn the computer back on the computer will do it's normal boot and the
little green bars will pop up and everything looks fine however, after the
little green bars go away im left with a black screen and might i add, with
no curser.
i look at my hard drive light and see that there is no action going on and
it just sits there. what do i need to do to get windows vista to boot and
load fully.
thanks for your help!!
jason