http://www.slipstick.com/addins/calendar_dates.asp - calendar update should
offer something.

If you just want numbers and can "think" about what phase it is, use a
Hebrew lunar as an alternate calendar. It numbers the days from 1 - 28. 14
is full moon.  It will display the month and day in Hebrew too.

you may also want to consider a windows utility - there are several tray
utilities that display a moon icon in the tray/notification area. Some
weather and time utilities also include the moon phase.