G'day
No need to bring them in we already here! Jk,
By what you've just told me I can say with confidence you have a virus. Congratulations! No really, you do. You've got a virus which deletes your notepad files then puts itself in as the files it deleted. So you look in the folder where notepad is and everythink looks the same rite? Well its not unfortunately, you'll have to if you don't already get a virus scanner, I recommend going to
www.trendmicro.com and running there free virus scanner.
If you need help on removing the virus, just giz us a hoy captain;) ;D
Regards~