One day, I got an annoying message saying "Your password has expired". Wtf?
Anyway, to disable the password expiry feature:
- open a command prompt in Administrator mode.
- Then type "lusrmgr.msc" to load up the "Local Users and Groups" management console.
- Go into "Users" and edit the profile that has expired.
- Select "Password never expires" and apply.
If you get "Access is denied", that means you didn't run the console with administrative rights (step #1).
While you're at it, you might want to take the time to disable the Guest account as well.