My laptop will not startup

Hello I have a Toshiba satellite 500 with windows vista home premium on it and for some reason it won't start up??
when I press the power on button it loads as normal going to the Toshiba leading innovation screen and down the bottom it has for setup press F2 and press F8 to boot device selection menu then the screen changes, it has a black background and it says ( `I believe this is called 'WINDOWS DOS' but I'm not certain')

Windows Error Recovery

Windows failed to start. A recent hardware or software change might be the cause

If windows files have been damaged or configured incorrectly startup repair can help diagnose and fix the problem. If power was interrupted during startup, choose start windows normally
(Use the arrow keys to highlight your choice.)

Launch startup repair (recommended)
Start windows normally.

when I choose startup repair it goes to a screen and says that windows is loading files and a bar loads down the bottom of the screen, then changes to the normal screen with ©Microsoft Corporation down the bottom and a loading bar just above it, then the screen changes to black and eventually a mouse cursor appears and that's as far as it gets. (I left it like that all day thinking maybe its loading files or something but still left with the same screen.)
Then when I choose start windows normally it goes straight to the ©Microsoft Corporation screen with the bar loading above it and it doesn't change from there, can you help me fix it please.