Posted almost daily on the Outlook groups - do NOT use the "import/export"
function for the transfer of data between two installations of Outlook.
Why?
(Courtesy of Russ Valentine [MVP-Outlook])
Importing an entire PST may well corrupt your profile and may create a ghost
PST that you can't close. Importing PST's will lose:
1.  Custom Forms
2.  Custom Views
3.  Connections between contacts and activities
4.  Received dates on mail
5.  Birthdays and anniversaries in calendar
6.  Journal connections
7.  Distribution Lists

Opening a PST file will preserve all of these. That is why we do not advise
people to import a native file into Outlook.

Here's how to do it:
On Old Computer:
Close Outlook.
Search for, and copy the pst file. Default name and location are:
C:\Documents and Settings\{Your User Name here}\Local Settings\Application
Data\Microsoft\Outlook\Outlook.pst. (You may have to enable Hidden and
System files in your search)

On the New computer:
Copy the pst file to your HDD. Do NOT overwrite any existing file. Remove
any read-only attribute. (Right-Click-Properties).
Open Outlook.
Do File-Open-Outlook Data File and navigate to where you copied the file.

You then have two alternatives.
1. Drag and drop the data from the old file to the new
or,
2. If you have a large amount of data, and the pst file you have copied is
in 2003/2007 format then you can set the old file as the Default Delivery
location and Outlook will just carry on using that file.
(Control Panel-Mail-Data File)

more info here:

http://www.slipstick.com/config/backup.htm
http://www.howto-outlook.com/Howto/backupandrestore.htm
http://office.microsoft.com/en-us/assistance/HA010771141033.aspx

HTH