Google seems to be denying that (unless paper is involved) there's any such thing as a 'notepad', which makes it rather difficult for me to answer your question!
However, if I can assume
(a) that you're referring to a notebook (or similar); and
(b) that it's running a version of Windows
then I suggest running System Restore to take the device's registry back to a date just before the problem first arose.
In Windows XP the route to get to System Restore is Start > Programs > Accessories > System Tools > System Restore. It's broadly similarly in other versions of Windows.