Edited - in case you read my original post, here's the easy way!
1) From your Address Book (click on "Addresses"), select File/Export/Address Book
2) Choose the A: drive
3) Do your upgrade
4) Open Outlook
5) File/Import/Address Book
For some reason, export does not work (at least on my system) unless you are actually viewing the address book, hence my more complex instructions on the original post.
I suggest you test this works before you upgrade, by exporting as above, renaming the original *.wab file ("search for *.wab) then make sure import returns all your addresses. Better to be safe than sorry!
[ 23 October 2001: Message edited by: sanjosebaz ]