Are you exporting your pst file from your original Outlook installation or just copying the pst file off of your hard drive? I would actually export your mail and contacts from Outlook using the export wizard and then try to import them into your current Outlook installation.
If you cannot export your file because you don't have the original installation of Outlook on your computer then you can try to repair your pst file and try to import it again.
If your current Outlook installation is an older version of the one that your pst file is from then that may cause a problem too. Or if your pst file is too big as in over 2GB (depending on your version of Outlook) then sometimes Outlook has a problem with that as well. Also right click on your pst file and go to Properties and make sure its not set to read only. If you are trying to import it from a CD then copy it to the hard drive first and then try to import it.