Everytime we download mail, we get an icon that appears in the toolbar
by the clock.  The icon is animated.  Mousing over the icon it says:

Microsoft Office Outlook is synchronizing folders.

This synchronizing causes the PC to hang.  

Please can you tell us how to stop the synchronizing of folders.  We
are running Outlook with just POP3s.  Not an exchange server.  We've
read a lot of links on how to do it, but it leads us to the same
issues: unchecking things in the advanced settings.  If you are
willing to take the time to answer, please could you try the procedure
out on  PC that is running Outlook 2003 and just accesing POP3
accounts, but not on an exchange server?  A lot of the aswers we have
seen are from people using Excahnge servers.  We are totally stuck on
this one.  Please... help...

The main thing I would try to do is clean out and organize into
seperate folders your INBOXes. I am assuming you've been all over the
offline and online synchronization settings. If cleaning out the mail
doesn't work, and you can't locate the corrupt mail, are you accessing
more than one account in the profile? If so, set up a new profile, and
use only one of the accounts. Does it work then? That should tell you
which account contains an offending email.

Just a question, would you happen to be using rules (Rules & Alerts)?
I have the same issue when I use rules and I just don't use rules
anymore.
If you disable all the rules (uncheck them), does the synchronization work?

If so, there is your problem, unfortunately, I do not know how to make
the rules work.