Outlook 2000

Hi there, we’re using POP3 email accounts and we’re downloading all our emails and the pst file is stored on the local drives. One of our users .pst file is 1,412,960KB big. I know that’s huge but he definitely wants to keep record of all those emails. He does archive but that doesn’t seem to change the file size. His outlook takes ages to start and will crash quite often. I’ve told him it must be the file size but I’m not that technical to know for sure and I don’t think he really believes me that the file size is causing the problems. Why doesn’t the file size decreases when he archives? Can anybody give me a good technical explanation why he has this problems and if there’s maybe a solution to decrease the file size when he archives. Many thanks.