If you can get into Safe Mode, it may be your only option to just do a factory restore on the laptop.
Before that though, are you running the most recent updates for Vista? I believe Service Pack 2 is the final pack for it. If you have all the updates and you're still having problems, you'll probably have little to no choice apart from a factory reset... But there is some good news that comes along with that as well. If you've got a bit of extra cash (and the hardware resources) you'd be much better off to simply upgrade to Windows 7 if you have to restore the operating system anyway. It'll take around the same amount of time (with minimal user input) to install Win 7 as it would to factory restore Vista, and you'd be losing all of...