[Outlook] Copy mail folder to another computer W7

Hi guys, Two W7 computers, lappy has Outlook 2003 desktop has Outlook 2010. How do I copy a particular mail storage folder from 2003 to 2010 and have it merge with, not overwrite, the old folder? I can have two folders if necessary but I want them all on one computer. Help!!!!!! -- "While you can teach an old dog new tricks, you simply can't teach him to be a cat." "Are you my Mummy?"