The password expires warning appears normally 14 days
before the password expires.This is security related,that is the
cause i put it in the Acces Rights category.You can modify this
timeframe and decraese/increase the amount of days this warning
appears before the password expires.To do so navigate to:

- HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
\Windows NT\CurrentVersion\Winlogon\

Locate here in the right pane the entry :

PasswordExpiryWarning

If the entry is not there you need to create it.( right click in the
right pane , new , REG_DWORD [Dword Value] ).Name it as mentioned
above.

Doubleclick the entry and set it's value to the number of days
you want the warning message to appear before the password expires.

Note:
This is a local modification and it is possible that in an enterprise
environment it will be overwritten constantly by group policies !