First, try booting the computer in Safe Mode. In Windows 7 and earlier versions, boot the computer and quickly and repeatedly press F8 before Windows starts to load. If the computer is at all successful, you'll get a boot menu from which you can select Safe Mode.
Windows 8 is trickier. F8 or Shift-F8 might work. But it might not.
If you succeed in booting into Safe Mode, you can use Windows Explorer (File Explorer in Windows 8) to find the files and drag them to an external drive.
If that doesn't work, you'll have to remove the hard drive and get to it through another computer. This is a reasonably easy task, especially with a laptop. Check your model's documentation—which is almost certainly online—to see how.
Once you've removed the drive, use a SATA-USB adapter to turn it temporarily into an external drive, so you can connect to it to another computer.