Outook 2000 pst files keep growing

I’m running Windows 2000 with Outlook 2000. I’ve got over 600 email address records (contacts) and continually delete junk mail as well as sent mail messages that are fulfilled. I have delete on exit to make sure deleted items are not in the trash bin (deleted records). My Inbox/Sent has a pretty constant 400 – 600 emails and appended files are saved in seperate (Word, Excel, Power Point) folders then deleted from the Inbox. Outlooks pst file keeps getting bigger (Archive.pst started out at about 25 MB and is now 49MB, and the above numbers of contacts and Inbox/sent are pretty constant) and bigger with all the foregoing. What is causing this and how can I change the settings to reduce the size of the archive.pst file?