Outlook 2000 export

From time to time we swap around computers here. We run Office 2000 suit. Question on some computers when exporting a Outlook.pst file it’s quick and on some it can take over an hour. Can anynoe suggest some of the setting I should watch out for when exporting ?
Note: .pst file size is not my problem
Windows 2000 & 98 it doesn’t make a diff.
Thanks