There appears to be some confusion about this process. It is simple and painless, but it requies Outlook to be installed on the computer along with Thunderbird. The Thunderbird Outlook import filter needs outlook to provide the necessary services to reassemble the mails that outlook has pulled apart.
The short simple method is to install Thunderbird on your old computer, do the import of all the data, and then using Mozbackup Transfer all you data to the new computer. If you want to pay for data translation from outlook, there are a number of comercial operators that will sell you products that will do that, but if you want it for free, the above is really the only way.