i might be wrong, but if you install outlook 2010 on top of your 2000, your pst should still be there..
anyway you can find your pst here
C:\Documents and Settings\YOUR USER ACCOUNT\Local Settings\Application Data\Microsoft\Outlook
please do open all your hidden file settings…
In outlook 2010 go to file>open>outlook data file. If it does not default to the location where the 2000 pst is, then change it to the path given by jinteik. You should be able to open it. If not then go through the file>import and again change to the directory where the old pst file is located. Since you are on the same machine it will not matter that you did not do an export. That is only important if you are changing machines.