The best response is below:
loff13 is talking about importing the data file from Entourage X into Entourage 2008 which are both on his Mac computer. I bought a new Mac a couple of days ago and I had backed up my data on an external hard drive. After installing Entourage 2008 on my new machine I tried to import the data using the import feature. It says the the import finished but no data was transferred. I copied the Main Identity folder from X into 2008 but that did not work. The data base is not compatible. I tried a few other things but they did not work either. Exporting contacts will only export the Address Book but not your e-mail files. At this point, I am not sure the best way to proceed. I will try other options and see what happens. I can't believe MS did not try to do this first before putting this out.
So essentially what you should do is re-install office X entourage, then import your old data into MacMail and ditch entourage altogether.
wicked, thanks a bunch Microsoft.