Try starting the laptop again, and as soon as it's started booting up, press and hold down the F8 button.
This should bring up the Windows advanced options menu, and using the arrow keys on the keyboard, highlight "safe mode" start up.
This will start your computer with the minimum drivers and running processes to get it going.
If this works and you've recently installed any new drivers or hardware, see if you can remove them then shut down the computer and try a restart without safe mode.
Sometimes doing a safe start followed by a shutdown and a normal start seems to clear the problem.