Outlook 2003 creating a pst

[crazychicken]

I have always wondered about this - maybe someone can shed some light:

After you create a backup pst file in Outlook 2003, say c:\backup.pst, if you try to COPY (not CUT) the file to an external drive, it complains that the file is in use. If you close Outlook, you can then copy the file. That doesn't make any sense to me... Outlook should not be using the file anymore once it is created, right? Has anyone else seen this happen?

Thanks,

David