Go to the Today Screen in Outlook 2003. To do this, lockate the Folders icon
on the bottom left hand corner of your screen (It's in the middle, 2nd from
the left; the left-most icon is Notes). When you click on Folders, go to the
very top of your screen where it has your name (if you configured Outlook to
send/receive mail; if not, it will just say "Personal Folders"). When you
click on your name, it should jump to the today screen.

The Today screen will gray out the appointments in the past for that day.
For example, if you had an engagement from 6:00a to 7:00a (say, "Gym") and
it's now 8:00a, the Gym appointment will be grayed out. All other active
appointments are in normal, black font.

I use a Dell Axim X50v running Pocket PC 2003 SE and if you go to the agenda
view screen it will show you the same view of all your current appointments
in black and the past appointments in gray. That way you can still see what's
due and what you've done without deleting anything.

Hope this helps!

Make them tasks instead of appointments.