I just got a Treo 700wx and did not have any previous experiance with
Windows Mobile or any other smartphone or PDA. I put about 20 personal
contacts into the phone and sync-ed with my office and home computers
to back up the contact
information into Outlook. A friend of mine had a much larger set of
contacts(many of which I needed) in their phone so I built a .pst file
from
their contacts and imported their contacts into Outlook on my home
computer. My sync cable to my phone was connected at this particular
moment and
although I got all of their contacts everything in my phone was
replaced by my friends info so I lost my 20 contacts( and a small
number
of appointments). The next day at the office I made a paper copy of
the 20 contacts in my office computer and then retyped each one into
my phone before sync-ing which, of course, worked. What should I have
done to merge the contacts other than typing them all in again?

first, a good backup program such as spb's
http://www.spbsoftwarehouse.com/ will pay for itself with one such event.

wm5+ made syncing problematic, and I don't know it, but check what
"rules" you have set in activesync.

Worst case senario, you can remove the pc's outlook pst, sync to get a
copy of the ppc contacts on the pc, merge on the pc, then resync...
since loosing the ppc contacts is a possibility in this scenario, the
backup assures you can restore and sync again.

Beverly Howard [MS MVP-Mobile Devices]