Can I delete my outlook database and start over??

I recently bought a Treo 750 on my AT&T plan
I have been using ACT for contacts and Calendar, and would like to
continue to do so for the time being until I can plan an orderly
migration to outlook
I imported cleaned up a copy of ACT deleting calendar and phone
entries I did not need on the phone, imported that file to outlook,
and sync'ed with the phone 1st time, and all was well.
But, then updated revised calendar entries from act to outlook and I
created duplicates.
Bottom line I hosed the outlook file and can't figure out how to
delete all the dup entries and I would like to start over.
Is there a way?

I have several outlook (,pst) files but I believe the one treo uses
is the outlook.pst file, but I have not figured out where that
setting is made. Help confirming that appreciated as well.

Also, I am using outlook 2003. will 2007 work with windows mobile 5? would I
be better of loading 2007 and starting with that?

Thanks

Jim Kelly
Mission Viejo