unable to import emails from Outlook 2000 to Thunderbird

I am trying to import emails from Outlook 2000 to Thunderbird. Current version of Thunderbird does not seem to recognize Outlook 2000. Someone suggested importing to Thunderbird 2.0.0.6. Where should I download it from without picking up viruses? Someone suggested importing the emails to Outlook 2007 trial version and then importing to Thunderbird. Where can I find trial version of Outlook 2007 without viruses.