Frankly, I am shocked that Microsoft don’t have a method of doing this. But, oh well…
In order to convert from using Outlook on a Mac to using Outlook on a PC, you can either use a really expensive one, like the one you will probably find easiest in Google, or you can use the software I did: Emailchemy.
For a relatively cheap purchase of $29.95 for a single-user license I was able to tell the software I was converting from OLM (exported from Outlook on the Mac) and select IMAP for output.
It converted the emails (over 10,000) and gave me a folder. I opened the Emailchemy Toolbox, selected IMAP import server, selecting that folder and starting the server.
All I had to do now was enter the server and user information Emailchemy had setup into Outlook, it was then able to access the emails on the localhost server. I then simply selected the emails and folders from the imported inbox, and dragged them into the local inbox under Personal Folders (PST), although it’s quite likely you could just export the IMAP folder to PST within Outlook for re-importing or storage, too.
Note: because some people may forget, never forget to copy your sent items. Also, never delete your original OLM file until you are sure you have a fully working copy in the new location. Lastly, always backup your OLM and PST files, and I recommend Carbonite for that. As always, I’m not responsible for you messing this up.