You cannot read the pst file in Windows Live Mail. You should have imported your data from Outlook 2000 to Outlook Express or exported it from Outlook 2000 as csv files.
If you still have the old computer you could do this now. If not, Google for “read pst” and you should find applications which can read pst files and export the data from them. You can then import the data to Windows Live Mail.
An alternative is to install a trial version of Outlook 2010, export the data and then uninstall the trial.