From memory, you make folders on your Desktop on the PC with names corresponding to all your email account's folder names (Inbox, Sent, whatever). Then, open each folder in Outlook (or Outlook Express), select all the emails and drag them into the corresponding folder. Once all your emails are stored on the Desktop, get those files onto a Mac using a network, some intermediate media (iPod, external drive or whatever), create new folders in your Entourage or Mail program and drag the emails back from these folders in Finder to your email app. I'm pretty sure that's it. 🙂