Compacting a PST file (Outlook 2002/2003)
After you've cleaned out your mailbox, you'd expect that the natural result would be for the file size of your PST file to decrease. Outlook will automatically compact the file if the difference in size will be more than 20 percent. If it's less, however, you'll want to manually compact the file. To do so, right-click on the Outlook Today icon in your Folder List or on the Outlook bar and choose Properties. Click the Advanced button, and then click Compact Now in the Personal Folders dialog box. Outlook then compacts your PST file. Click OK twice to close the open dialog boxes.