Cannot copy Outlook:

[Klassy]

I am trying to copy my Outlook 2003 pst file from my laptop to my home office
PC. The laptop has more info on it than the PC. I have licenced copies of
Office 2003 Pro (laptop) and Office 2003 standard (PC). I tried coping the
outlook.pst file from the laptop to my PC and received the following message:
"Cannot copy Outlook: The process cannot access the file because another
process has locked a portion of the file." I have downloaded and installed
the "Backup" add-in to both. It worked on the PC, but on the Laptop I
received the same message, as above.

Has anybody had this problem or know how to "unlock" the file??

Thanks for your help....