Try running System Restore to take your laptop's registry back to a date before the problem occurred. (If you've installed any software in the intervening period, you'll need to reinstall it. However you won't lose any files created since the restore date, such as Word documents, image files or emails).
Instructions for XP are here:
http://support.microsoft.com/kb/306084
For Vista, see here:
http://windowshelp.microsoft.com/windows/en-us /help/9f6d755a-74bb-4a7d-a625-d762dd8e79e51033 .mspx
Chris